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The GNU General Public License (GNU GPL or simply GPL) is a series of widely used
free software license A free-software license is a notice that grants the recipient of a piece of software extensive rights to modify and software distribution, redistribute that software. These actions are usually prohibited by copyright law, but the rights-holde ...
s that guarantee
end user In product development, an end user (sometimes end-user) is a person who ultimately uses or is intended to ultimately use a product. The end user stands in contrast to users who support or maintain the product, such as sysop A sysop (; an abbrev ...
s the
four freedoms The Four Freedoms were goals articulated by U.S. President The president of the United States (POTUS) is the head of state A head of state (or chief of state) is the public persona who officially embodies a state (polity), state#Fo ...
to run, study, share, and modify the software. The licenses were originally written by
Richard Stallman Richard Matthew Stallman (; born March 16, 1953), also known by his initials, rms, is an American free software movement The free software movement is a social movement A social movement is a loosely organized effort by a large group of peo ...

Richard Stallman
, founder of the
Free Software Foundation The Free Software Foundation (FSF) is a 501(c)(3) A 501(c)(3) organization is a corporation, trust, unincorporated association, or other type of organization exempt from federal income tax under section 501(c)(3) of Title 26 of the United States ...
(FSF), for the
GNU Project The GNU Project () is a free software Free software (or libre software) is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versi ...
, and grant the recipients of a
computer program In imperative programming, a computer program is a sequence of instructions in a programming language that a computer can execute or interpret. In declarative programming, a ''computer program'' is a Set (mathematics), set of instructions. A comp ...
the rights of
the Free Software Definition The Free Software Definition written by Richard Stallman Richard Matthew Stallman (; born March 16, 1953), also known by his initials, rms, is an American free software movement activist and programmer A computer programmer, sometimes cal ...
. The GPL series are all
copyleft Copyleft is the practice of granting the right to freely distribute and modify with the requirement that the same rights be preserved in derivative works created from that property. Copyleft in the form of s can be used to maintain conditions ...

copyleft
licenses, which means that any
derivative work In copyright law Copyright is a type of intellectual property that gives its owner the exclusive right to make copies of a creative work, usually for a limited time. The creative work may be in a literary, artistic, educational, or musical ...
must be distributed under the same or equivalent license terms. This is in distinction to
permissive software license A permissive software license, sometimes also called BSD-like or BSD-style license, is a free-software license A license (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. E ...
s, of which the
BSD licenses BSD licenses are a family of permissive free software license A permissive software license, sometimes also called BSD-like or BSD-style license, is a free-software license with only minimal restrictions on how the software can be used, modi ...
and the MIT License are widely used, less restrictive examples. GPL was the first copyleft license for general use. Historically, the GPL license family has been one of the most popular software licenses in the
free and open-source software Free and open-source software (FOSS) is software Software is a collection of instructions that tell a computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. ...
domain. Prominent free software programs licensed under the GPL include the
Linux kernel The Linux kernel is a free and open-source Free and open-source software (FOSS) is software that is both free software and open-source software where anyone is free software license, freely licensed to use, copy, study, and change the softwar ...
and the
GNU Compiler Collection The GNU Compiler Collection (GCC) is an optimizing compiler In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithm of an ...
(GCC). David A. Wheeler argues that the copyleft provided by the GPL was crucial to the success of
Linux Linux ( or ) is a family of open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product ...

Linux
-based systems, giving the programmers who contributed to the kernel the assurance that their work would benefit the whole world and remain free, rather than being exploited by software companies that would not have to give anything back to the community. In 2007, the third version of the license (GPLv3) was released to address some perceived problems with the second version (GPLv2) which were discovered during the latter's long-time usage. To keep the license up to date, the GPL license includes an optional "any later version" clause, allowing users to choose between the original terms or the terms in new versions as updated by the FSF. Developers can omit it when licensing their software; the Linux kernel, for instance, is licensed under GPLv2 without the "any later version" clause.


History

The GPL was written by
Richard Stallman Richard Matthew Stallman (; born March 16, 1953), also known by his initials, rms, is an American free software movement The free software movement is a social movement A social movement is a loosely organized effort by a large group of peo ...

Richard Stallman
in 1989, for use with programs released as part of the GNU project. The original GPL was based on a unification of similar licenses used for early versions of
GNU Emacs GNU Emacs is a free software text editor. It was created by GNU Project founder Richard Stallman. In common with other varieties of Emacs, GNU Emacs is extensible using a Turing complete programming language. GNU Emacs has been called "the most p ...
(1985), the
GNU Debugger The GNU Debugger (GDB) is a Software portability, portable debugger that runs on many Unix-like systems and works for many programming languages, including Ada (programming language), Ada, C (programming language), C, C++, Objective-C, Free Pasc ...
, and the
GNU C Compiler The GNU Compiler Collection (GCC) is an optimizing compiler In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes a ...
. These licenses contained similar provisions to the modern GPL, but were specific to each program, rendering them incompatible, despite being the same license. Stallman's goal was to produce one license that could be used for any project, thus making it possible for many projects to share code. The second version of the license, version 2, was released in 1991. Over the following 15 years, members of the
free software community The free software movement is a social movement Social organisms, including humans, live collectively in interacting populations. This interaction is considered social whether they are aware of it or not, and whether the exchange is Volition (psy ...
became concerned over problems in the GPLv2 license that could let someone exploit GPL-licensed software in ways contrary to the license's intent. These problems included
tivoization Tivoization is the creation of a system that incorporates software Software is a collection of instructions that tell a computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ...
(the inclusion of GPL-licensed software in hardware that refuses to run modified versions of its software), compatibility issues similar to those of the
Affero General Public License The Affero General Public License (Affero GPL and informally Affero License) is a free software license. The first version of the Affero General Public License (AGPLv1), was published by Affero, Inc. in March 2002, and based on the GNU General Publ ...
, and patent deals between
Microsoft Microsoft Corporation is an American multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational force, a military body from multiple countries * Multination ...

Microsoft
and distributors of free and open-source software, which some viewed as an attempt to use patents as a weapon against the free software community. Version 3 was developed to attempt to address these concerns and was officially released on 29 June 2007.


Version 1

Version 1 of the GNU GPL, released on 25 February 1989, prevented what were then the two main ways that software distributors restricted the freedoms that define free software. The first problem was that distributors may publish
binary file 290px, A hex dump of the 318 byte Wikipedia favicon">byte.html" ;"title="hex dump of the 318 byte">hex dump of the 318 byte Wikipedia favicon, or . The first column numerates the line's starting address, while the * indicates repetition. A bina ...

binary file
s only—executable, but not readable or modifiable by humans. To prevent this, GPLv1 stated that copying and distributing copies or any portion of the program must also make the human-readable source code available under the same licensing terms. The second problem was that distributors might add restrictions, either to the license or by combining the software with other software that had other restrictions on distribution. The union of two sets of restrictions would apply to the combined work, thus adding unacceptable restrictions. To prevent this, GPLv1 stated that modified versions, as a whole, had to be distributed under the terms in GPLv1. Therefore, software distributed under the terms of GPLv1 could be combined with software under more permissive terms, as this would not change the terms under which the whole could be distributed. However, software distributed under GPLv1 could not be combined with software distributed under a more restrictive license, as this would conflict with the requirement that the whole be distributable under the terms of GPLv1.


Version 2

According to Richard Stallman, the major change in GPLv2 was the "Liberty or Death" clause, as he calls it – Section 7. The section says that licensees may distribute a GPL-covered work ''only'' if they can satisfy all of the license's obligations, despite any other legal obligations they might have. In other words, the obligations of the license may not be severed due to conflicting obligations. This provision is intended to discourage any party from using a
patent infringement A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of years in exchange for publishing an sufficiency of disclosure, enabling discl ...
claim or other litigation to impair users' freedom under the license. By 1990, it was becoming apparent that a less restrictive license would be strategically useful for the
C library The C standard library or libc is the standard library A standard library in computer programming Computer programming is the process of designing and building an executable computer program to accomplish a specific computing result or to per ...
and for software libraries that essentially did the job of existing proprietary ones; when version 2 of the GPL (GPLv2) was released in June 1991, therefore, a second license – the GNU Library General Public License – was introduced at the same time and numbered with version 2 to show that both were complementary. The version numbers diverged in 1999 when version 2.1 of the LGPL was released, which renamed it the
GNU Lesser General Public License The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...
to reflect its place in the philosophy. The GPLv2 was also modified to refer to the new name of the LGPL, but its version number remained the same, resulting in the original GPLv2 not being recognised by the Software Package Data Exchange (SPDX). The license includes instructions to specify "version 2 of the License, or (at your option) any later version" to allow the flexible optional use of either version 2 or 3, but some developers change this to specify "version 2" only.


Version 3

In late 2005, the
Free Software Foundation The Free Software Foundation (FSF) is a 501(c)(3) A 501(c)(3) organization is a corporation, trust, unincorporated association, or other type of organization exempt from federal income tax under section 501(c)(3) of Title 26 of the United States ...
(FSF) announced work on version 3 of the GPL (GPLv3). On 16 January 2006, the first "discussion draft" of GPLv3 was published, and the public consultation began. The public consultation was originally planned for nine to fifteen months, but finally stretched to eighteen months with four drafts being published. The official GPLv3 was released by the FSF on 29 June 2007. GPLv3 was written by Richard Stallman, with legal counsel from
Eben Moglen Eben Moglen (born 1959) is an American legal scholar who is professor Professor (commonly abbreviated as Prof.) is an academic An academy (Attic Greek: Ἀκαδήμεια; Koine Greek Ἀκαδημία) is an institution of secondary educa ...
and Richard Fontana from the
Software Freedom Law Center The Software Freedom Law Center (SFLC) is an organization that provides '' pro bono'' legal representation and related services to not-for-profit developers of free software Free software (or libre software) is computer software Software ...
. According to Stallman, the most important changes were in relation to
software patents A software patent is a patent NPOV disputes from March 2021 A patent is a Title (property), title that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of years in exchange fo ...
,
free software license A free-software license is a notice that grants the recipient of a piece of software extensive rights to modify and software distribution, redistribute that software. These actions are usually prohibited by copyright law, but the rights-holde ...
compatibility, the definition of "source code", and
hardware restrictions A hardware restriction (sometimes called hardware DRM) is content protection enforced by electronic component An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their as ...
on software modifications, such as
tivoization Tivoization is the creation of a system that incorporates software Software is a collection of instructions that tell a computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ...
.Interview with Richard Stallman
, Free Software Magazine, 23 January 2008.
Other changes related to internationalization, how license violations are handled, and how additional permissions could be granted by the copyright holder. The concept of "software propagation", as a term for the copying and duplication of software, was explicitly defined. The public consultation process was coordinated by the Free Software Foundation with assistance from Software Freedom Law Center,
Free Software Foundation Europe The Free Software Foundation Europe (FSFE) is an '' eingetragener Verein'' (registered voluntary association) under German law The law of Germany (german: das Recht Deutschlands), that being the modern German legal system (german: Deutsches Re ...
, and other free software groups. Comments were collected from the public via the gplv3.fsf.org web portal, using purpose-written software called stet. During the public consultation process, 962 comments were submitted for the first draft. By the end of the comment period, a total of 2,636 comments had been submitted. The third draft was released on 28 March 2007. This draft included language intended to prevent patent-related agreements such as the controversial Microsoft-Novell patent agreement, and restricted the anti-tivoization clauses to a legal definition of a "user" and a "consumer product". It also explicitly removed the section on "Geographical Limitations", whose probable removal had been announced at the launch of the public consultation. The fourth discussion draft, which was the last, was released on 31 May 2007. It introduced Apache License version 2.0 compatibility (prior versions are incompatible), clarified the role of outside contractors and made an exception to avoid the perceived problems of a Microsoft–Novell style agreement, saying in Section 11 paragraph 6 that: This aimed to make future such deals ineffective. The license was also meant to cause Microsoft to extend the patent licenses it granted to Novell customers for the use of GPLv3 software to ''all'' users of that GPLv3 software; this was possible only if Microsoft was legally a "conveyor" of the GPLv3 software. Early drafts of GPLv3 also let licensors add an
Affero The Affero General Public License (Affero GPL and informally Affero License) is a free software license. The first version of the Affero General Public License (AGPLv1), was published by Affero, Inc. in March 2002, and based on the GNU General Publ ...
-like requirement that would have plugged the ''
ASP ASP may refer to: Combat * ASP pistol * ASP, Inc., law enforcement weapon manufacturer ** A type of extending baton * Ammunition supply point or ammunition dump An ammunition dump, ammunition supply point (ASP), ammunition handling area (AHA ...
loophole in the GPL''.List of free-software licences on the FSF website
"We recommend that developers consider using the GNU AGPL for any software which will commonly be run over a network."
As there were concerns expressed about the administrative costs of checking code for this additional requirement, it was decided to keep the GPL and the Affero license separated. Others, notably some high-profile
Linux kernel The Linux kernel is a free and open-source Free and open-source software (FOSS) is software that is both free software and open-source software where anyone is free software license, freely licensed to use, copy, study, and change the softwar ...
developers such as
Linus Torvalds Linus Benedict Torvalds ( , ; born 28 December 1969) is a Finnish-American software engineer who is the creator and, historically, the main developer of the Linux kernel, used by Linux distributions and other operating systems such as Android (o ...
,
Greg Kroah-Hartman Greg Kroah-Hartman (GKH) is a major Linux kernel The Linux kernel is a free and open-source Free and open-source software (FOSS) is software Software is a collection of Instruction (computer science), instructions and data (computing), ...
, and , commented to the mass media and made public statements about their objections to parts of discussion drafts 1 and 2. The kernel developers referred to GPLv3 draft clauses regarding
DRM DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement militaire ...
/
Tivoization Tivoization is the creation of a system that incorporates software Software is a collection of instructions that tell a computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ...
, patents, and "additional restrictions", and warned of a
Balkanisation Balkanization refers to the fragmentation, or sub-fragmentation, of a larger region or state into smaller regions or states, which may be hostile or uncooperative with one another. When sponsored or encouraged by a sovereign third party, the term ...
of the "Open Source Universe". Linus Torvalds, who decided not to adopt the GPLv3 for the Linux kernel, reiterated his criticism several years later. GPLv3 improved compatibility with several free software licenses such as the Apache License, version 2.0, and the GNU Affero General Public License, which GPLv2 could not be combined with. However, GPLv3 software could only be combined and share code with GPLv2 software if the GPLv2 license used had the optional "or later" clause and the software was upgraded to GPLv3. While the "GPLv2 or any later version" clause is considered by FSF as the most common form of licensing GPLv2 software,
Toybox Toybox is a free and open-source software Free and open-source software (FOSS) is software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to work. This is in con ...
developer Rob Landley described it as a ''lifeboat clause''. Software projects licensed with the optional "or later" clause include the
GNU Project The GNU Project () is a free software Free software (or libre software) is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versi ...
, while a prominent example without the clause is the Linux kernel. The final version of the license text was published on 29 June 2007.


Terms and conditions

The terms and conditions of the GPL must be made available to anybody receiving a copy of the work that has a GPL applied to it ("the licensee"). Any licensee who adheres to the terms and conditions is given permission to modify the work, as well as to copy and redistribute the work or any derivative version. The licensee is allowed to charge a fee for this service or do this free of charge. This latter point distinguishes the GPL from software licenses that prohibit commercial redistribution. The FSF argues that free software should not place restrictions on commercial use, and the GPL explicitly states that GPL works may be sold at any price. The GPL additionally states that a distributor may not impose "further restrictions on the rights granted by the GPL". This forbids activities such as distributing the software under a non-disclosure agreement or contract. The fourth section for version 2 of the license and the seventh section of version 3 require that programs distributed as pre-compiled binaries be accompanied by a copy of the source code, a written offer to distribute the source code via the same mechanism as the pre-compiled binary, or the written offer to obtain the source code that the user got when they received the pre-compiled binary under the GPL. The second section of version 2 and the fifth section of version 3 also require giving "all recipients a copy of this License along with the Program". Version 3 of the license allows making the source code available in additional ways in fulfillment of the seventh section. These include downloading source code from an adjacent network server or by peer-to-peer transmission, provided that is how the compiled code was available and there are "clear directions" on where to find the source code. The FSF does not hold the copyright for a work released under the GPL unless an author explicitly
assigns copyrights An assignment is a legal term used in the context of the law of contract and of property (law), property. In both instances, assignment is the process whereby a person, the ''assignor'', transfers rights or benefits to another, the ''assignee''. An ...
to the FSF (which seldom happens except for programs that are part of the GNU project). Only the individual copyright holders have the authority to sue when a license violation is suspected.


Use of licensed software

Software under the GPL may be run for all purposes, including commercial purposes and even as a tool for creating
proprietary software Proprietary software, also known as non-free software or closed-source software, is computer software for which the software's publisher or another person reserves some rights from licenses to use, modify, share modifications, or share the softwa ...
, such as when using GPL-licensed
compiler In computing, a compiler is a computer program that Translator (computing), translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily ...

compiler
s. Users or companies who distribute GPL-licensed works (e.g. software), may charge a fee for copies or give them free of charge. This distinguishes the GPL from
shareware Shareware is a type of proprietary software which is initially shared by the owner for trial use at little or no cost with usually limited functionality or incomplete documentation but which can be upgraded upon payment. Shareware is often offered ...
software licenses that allow copying for personal use but prohibit the commercial distribution or proprietary licenses where copying is prohibited by
copyright law Copyright is a type of intellectual property that gives its owner the exclusive right to copy and distribute a creative work, usually for a limited time. The creative work may be in a literary, artistic, educational, or musical form. Copyrigh ...
. The FSF argues that freedom-respecting free software should also not restrict commercial use and distribution (including redistribution): In purely private (or internal) use—with no sales and no distribution—the software code may be modified and parts reused without requiring the source code to be released. For sales or distribution, the entire source code needs to be made available to end users, including any code changes and additions—in that case, copyleft is applied to ensure that end users retain the freedoms defined above. However, software running as an application program under a GPL-licensed operating system such as Linux is not required to be licensed under GPL or to be distributed with source-code availability—the licensing depends only on the used libraries and software components and not on the underlying platform. For example, if a program consists only of original
source code In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and ...

source code
, or is combined with source code from other
software component Component-based software engineering (CBSE), also called component-based development (CBD), is a branch of software engineering that emphasizes the separation of concerns In computer science Computer science deals with the theoretical founda ...
s, then the custom software components need not be licensed under GPL and need not make their source code available; even if the underlying operating system used is licensed under the GPL, applications running on it are not considered derivative works. Only if GPLed parts are used in a program (and the program is distributed), then all other source code of the program needs to be made available under the same license terms. The
GNU ''Lesser'' General Public License GNU () is an extensive collection of free software, which can be used as an operating system or can be used in parts with other operating systems. The use of the completed GNU tools led to the family of operating systems popularly known as Linu ...
(LGPL) was created to have a weaker copyleft than the GPL, in that it does not require custom-developed source code (distinct from the LGPL'ed parts) to be made available under the same license terms. The fifth section of version 3 states that no GPL-licensed code shall be considered an effective "technical protection measure" as defined by Article 11 of the
WIPO Copyright Treaty The World Intellectual Property Organization Copyright Treaty (WIPO Copyright Treaty or WCT) is an international treaty A treaty is a formal legally binding written agreement between actors in international law. It is usually entered into by ...
, and that those who convey the work waive all legal power to prohibit circumvention of the technical protection measure "to the extent such circumvention is effected by exercising rights under this License with respect to the covered work". This means that users cannot be held liable for circumventing DRM implemented using GPL v3-licensed code under laws such as the U.S.
Digital Millennium Copyright Act The Digital Millennium Copyright Act (DMCA) is a 1998 United States The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country Contiguous United States, primarily located in North Americ ...
(DMCA).


Copyleft

The distribution rights granted by the GPL for modified versions of the work are not unconditional. When someone distributes a GPL'ed work plus their own modifications, the requirements for distributing the whole work cannot be any greater than the requirements that are in the GPL. This requirement is known as copyleft. It earns its legal power from the use of
copyright Copyright is a type of intellectual property Intellectual property (IP) is a category of property Property is a system of rights that gives people legal control of valuable things, and also refers to the valuable things themselves. ...

copyright
on software programs. Because a GPL work is copyrighted, a licensee has no right to redistribute it, not even in modified form (barring
fair use Fair use is a doctrine in the law of the United States that permits limited use of copyrighted material without having to first acquire permission from the copyright holder. Fair use is one of the limitations to copyright intended to balance the ...
), except under the terms of the license. One is only required to adhere to the terms of the GPL if one wishes to exercise rights normally restricted by copyright law, such as redistribution. Conversely, if one distributes copies of the work without abiding by the terms of the GPL (for instance, by keeping the source code secret), they can be
sued A lawsuit is a proceeding by a party or parties against another in the civil Civil may refer to: *Civic virtue, or civility *Civil action, or lawsuit *Civil affairs *Civil and political rights *Civil disobedience *Civil engineering *Civil ...
by the original author under copyright law. Copyright law has historically been used to prevent distribution of work by parties not authorized by the creator. Copyleft uses the same copyright laws to accomplish a very different goal. It grants rights to distribution to all parties insofar as they provide the same rights to subsequent ones, and they to the next, etc. In this way the GPL and other copyleft licenses attempt to enforce
libre Libre may refer to: Computing * Libre software, free software * Libre Computer Project, developer of open-hardware single-board computers Music * Libre (Alejandra Guzmán album), ''Libre'' (Alejandra Guzmán album) * Libre (Jennifer Peña album), ...
access to the work and all derivatives. Many distributors of GPL'ed programs bundle the source code with the
executable In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and ...
s. An alternative method of satisfying the copyleft is to provide a written offer to provide the source code on a physical medium (such as a CD) upon request. In practice, many GPL'ed programs are distributed over the Internet, and the source code is made available over
FTP The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and data c ...
or
HTTP The Hypertext Transfer Protocol (HTTP) is an application layer An application layer is an abstraction layer that specifies the shared communications protocols and Interface (computing), interface methods used by Host (network), hosts in a c ...
. For Internet distribution, this complies with the license. Copyleft applies only when a person seeks to redistribute the program. Developers may make private modified versions with no obligation to divulge the modifications, as long as they do not distribute the modified software to anyone else. Copyleft applies only to the software, and not to its output (unless that output is itself a derivative work of the program). For example, a public web portal running a modified derivative of a GPL'ed
content management system A content management system (CMS) is a computer software used to manage the creation and modification of digital content (content management).''Managing Enterprise Content: A Unified Content Strategy''. Ann Rockley, Pamela Kostur, Steve Manning. Ne ...
is not required to distribute its changes to the underlying software, because its output is not a derivative. There has been debate on whether it is a violation of the GPL to release the source code in obfuscated form, such as in cases in which the author is less willing to make the source code available. The consensus was that while unethical, it was not considered a violation. The issue was clarified when the license was altered with v2 to require that the "preferred" version of the source code be made available.


License versus contract

The GPL was designed as a
license A license (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United States. Cur ...

license
, rather than a contract. In some
Common Law In law, common law (also known as judicial precedent or judge-made law, or case law) is the body of law created by judges and similar quasi-judicial tribunals by virtue of being stated in written opinions. ''Black's Law Dictionary'' is the most-us ...
jurisdictions, the legal distinction between a license and a contract is an important one: contracts are enforceable by
contract law A contract is a legally binding agreement that defines and governs the rights and duties between or among its parties Image:'Hip, Hip, Hurrah! Artist Festival at Skagen', by Peder Severin Krøyer (1888) Demisted with DXO PhotoLab Clearview; ...
, whereas licenses are enforced under
copyright law Copyright is a type of intellectual property that gives its owner the exclusive right to copy and distribute a creative work, usually for a limited time. The creative work may be in a literary, artistic, educational, or musical form. Copyrigh ...
. However, this distinction is not useful in the many jurisdictions where there are no differences between contracts and licenses, such as
Civil Law Civil law may refer to: * Civil law (common law) Civil law is a major branch of the law.Glanville Williams. ''Learning the Law''. Eleventh Edition. Stevens. 1982. p. 2. In common law legal systems such as England and Wales and the law of the United ...
systems. Those who do not accept the GPL's terms and conditions do not have permission, under copyright law, to copy or distribute GPL-licensed software or derivative works. However, if they do not redistribute the GPL'ed program, they may still use the software within their organization however they like, and works (including programs) constructed by the use of the program are not required to be covered by this license. Software developer
Allison Randal Allison Randal is a software developer and author. She was the chief architect of the Parrot virtual machine, a member of the board of directors for The Perl Foundation, a director of the Python Software Foundation from 2010 to 2012, and the ...

Allison Randal
argued that the GPLv3 as a license is unnecessarily confusing for lay readers, and could be simplified while retaining the same conditions and legal force. In April 2017, a US federal court ruled that an open-source license is an enforceable contract.


Derivations

The text of the GPL is itself
copyright Copyright is a type of intellectual property Intellectual property (IP) is a category of property Property is a system of rights that gives people legal control of valuable things, and also refers to the valuable things themselves. ...

copyright
ed, and the copyright is held by the Free Software Foundation. The FSF permits people to create new licenses based on the GPL, as long as the derived licenses do not use the GPL preamble without permission. This is discouraged, however, since such a license might be incompatible with the GPL and causes a perceived
license proliferation License proliferation is the phenomenon of an abundance of already existing and the continued creation of new software license A software license is a legal instrument (usually by way of contract law, with or without printed material) governin ...
. Other licenses created by the GNU project include the
GNU Lesser General Public License The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...
,
GNU Free Documentation License The GNU Free Documentation License (GNU FDL or simply GFDL) is a copyleft Copyleft is the practice of granting the right to freely distribute and modify intellectual property with the requirement that the same rights be preserved in derivat ...
, and
Affero General Public License The Affero General Public License (Affero GPL and informally Affero License) is a free software license. The first version of the Affero General Public License (AGPLv1), was published by Affero, Inc. in March 2002, and based on the GNU General Publ ...
. The text of the GPL is not itself under the GPL. The license's copyright disallows modification of the license. Copying and distributing the license is allowed since the GPL requires recipients to get "a copy of this License along with the Program". According to the GPL FAQ, anyone can make a new license using a modified version of the GPL as long as they use a different name for the license, do not mention "GNU", and remove the preamble, though the preamble can be used in a modified license if permission to use it is obtained from the Free Software Foundation (FSF).


Linking and derived works


Libraries

According to the FSF, "The GPL does not require you to release your modified version or any part of it. You are free to make modifications and use them privately, without ever releasing them." However, if one releases a GPL-licensed entity to the public, there is an issue regarding linking: namely, whether a proprietary program that uses a GPL library is in violation of the GPL. This key dispute is whether non-GPL software can legally statically link or dynamically link to GPL libraries. Different opinions exist on this issue. The GPL is clear in requiring that all
derivative work In copyright law Copyright is a type of intellectual property that gives its owner the exclusive right to make copies of a creative work, usually for a limited time. The creative work may be in a literary, artistic, educational, or musical ...
s of code under the GPL must themselves be under the GPL. Ambiguity arises with regards to using GPL libraries, and bundling GPL software into a larger package (perhaps mixed into a binary via static linking). This is ultimately a question not of the GPL ''per se'', but of how copyright law defines derivative works. The following points of view exist:


Point of view: dynamic and static linking violate GPL

The Free Software Foundation (which holds the copyright of several notable GPL-licensed software products and of the license text itself) asserts that an executable that uses a dynamically linked library is indeed a derivative work. This does not, however, apply to separate programs communicating with one another. The Free Software Foundation also created the
LGPL The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...
, which is nearly identical to the GPL, but with additional permissions to allow linking for the purposes of "using the library". Richard Stallman and the FSF specifically encourage library writers to license under the GPL so that proprietary programs cannot use the libraries, in an effort to protect the free-software world by giving it more tools than the proprietary world.


Point of view: static linking violates GPL but unclear as of dynamic linking

Some people believe that while
static linking In computer science Computer science deals with the theoretical foundations of information, algorithms and the architectures of its computation as well as practical techniques for their application. Computer science is the study of Algori ...
produces derivative works, it is not clear whether an executable that dynamically links to a GPL code should be considered a derivative work (see weak copyleft). Linux author Linus Torvalds agrees that dynamic linking can create derived works but disagrees over the circumstances. A
Novell Novell, Inc. was an American software and services company headquartered in Provo, Utah Provo is the third-largest city in Utah, United States. It is south of Salt Lake City along the Wasatch Front. Provo is the largest city and county se ...

Novell
lawyer has written that dynamic linking not being derivative "makes sense" but is not "clear-cut", and that evidence for good-intentioned dynamic linking can be seen by the existence of proprietary Linux kernel drivers. In '' Galoob v. Nintendo'', the United States
Ninth Circuit Court of Appeals The United States Court of Appeals for the Ninth Circuit (in case citation Case citation is a system used by legal professionals to identify past court case decisions, either in series of books called reporters or law reports, or in a neutral ...
defined a derivative work as having form' or permanence" and noted that "the infringing work must incorporate a portion of the copyrighted work in some form", but there have been no clear court decisions to resolve this particular conflict.


Point of view: linking is irrelevant

According to an article in the ''
Linux Journal ''Linux Journal'' (''LJ'') is a monthly technology magazine A magazine is a periodical literature, periodical publication which is printing, printed in Coated paper, gloss-coated and Paint sheen, matte paper. Magazines are generally published ...
'', Lawrence Rosen (a one-time
Open Source Initiative The Open Source Initiative (OSI) is the steward of the Open Source definition, Open Source Definition, the set of rules that define Open Source Software, open source software. It is a California public-benefit nonprofit corporation, with 501(c)(3 ...
general counsel) argues that the method of linking is mostly irrelevant to the question about whether a piece of software is a
derivative work In copyright law Copyright is a type of intellectual property that gives its owner the exclusive right to make copies of a creative work, usually for a limited time. The creative work may be in a literary, artistic, educational, or musical ...
; more important is the question about whether the software was intended to interface with client software and/or libraries.Lawrence Rosen
Derivative Works
''Linux Journal'' (1 January 2003).
He states, "The primary indication of whether a new program is a derivative work is whether the source code of the original program was used n a copy-paste sense modified, translated or otherwise changed in any way to create the new program. If not, then I would argue that it is not a derivative work," and lists numerous other points regarding intent, bundling, and linkage mechanism. He further argues on his firm's website that such "market-based" factors are more important than the linking technique. There is also the specific issue of whether a plugin or
module Module, modular and modularity may refer to the concept of modularity. They may also refer to: Computing and engineering * Modular design, the engineering discipline of designing complex devices using separately designed sub-components * Modula ...
(such as the
NVidia Nvidia CorporationOfficially written as NVIDIA and stylized in its logo as nVIDIA with the lowercase "n" the same height as the uppercase "VIDIA"; formerly stylized as ''n''VIDIA with a large italicized lowercase "n" on products from the mid 19 ...
or ATI
graphics card A graphics card (also called a video card, display card, graphics adapter, video adapter, or display adapter) is an expansion card Modern EEPROM chip suitable for storing expansion card configuration electronically In computing Compu ...
kernel module In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both computer hardware , hardware and software ...
s) must also be GPL, if it could reasonably be considered its own work. This point of view suggests that reasonably separate plugins, or plugins for software designed to use plugins, could be licensed under an arbitrary license if the work is GPLv2. Of particular interest is the GPLv2 paragraph: The GPLv3 has a different clause: As a case study, some supposedly proprietary plugins and
theme Theme or themes may refer to: * Theme (arts) In contemporary literary studies Literary criticism (or literary studies) is the study, evaluation Evaluation is a system A system is a group of Interaction, interacting or interrelated eleme ...
s/
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have differ ...
s for GPLv2
CMS #REDIRECT CMS #REDIRECT CMS CMS may refer to: Computing * Collection management system for a museum collection * Color management system, a system for computers to control the representation of colors * Content management system A content manage ...
software such as
Drupal Drupal () is a free and open-source Free and open-source software (FOSS) is software that is both free software and open-source software where anyone is free software license, freely licensed to use, copy, study, and change the software in an ...

Drupal
and
WordPress WordPress (WP, WordPress.org) is a free and open-source content management system A content management system (CMS)''Managing Enterprise Content: A Unified Content Strategy''. Ann Rockley, Pamela Kostur, Steve Manning. New Riders, 2003. is a ...

WordPress
have come under fire, with both sides of the argument taken. The FSF differentiates on how the plugin is being invoked. If the plugin is invoked through dynamic linkage and it performs function calls to the GPL program then it is most likely a derivative work.


Communicating and bundling with non-GPL programs

The mere act of communicating with other programs does not, by itself, require all software to be GPL; nor does distributing GPL software with non-GPL software. However, minor conditions must be followed that ensures the rights of GPL software are not restricted. The following is a quote from the gnu.org GPL
FAQ A frequently asked questions (FAQ) list is often used in articles, websites, email lists, and online forums where common questions tend to recur, for example through posts or queries by new users related to common knowledge gaps. The purpose ...

FAQ
, which describes to what extent software is allowed to communicate with and be bundled with GPL programs: The FSF thus draws the line between "library" and "other program" via 1) "complexity" and "intimacy" of information exchange and 2) mechanism (rather than semantics), but resigns that the question is not clear-cut and that in complex situations, case law will decide.


Legal status

The first known violation of the GPL was in 1989, when
NeXT NeXT, Inc. (later NeXT Computer, Inc. and NeXT Software, Inc.) was an American technology company that specialized in computer workstations A workstation is a special computer designed for technical or computational science, scientific appli ...
extended the GCC compiler to support
Objective-C Objective-C is a general-purpose, object-oriented Object-oriented programming (OOP) is a programming paradigm Program, programme, programmer, or programming may refer to: Business and management * Program management, the process of m ...
, but did not publicly release the changes. After an inquiry they created a public
patch Patch may refer to: Places * Patch, St. Louis, a neighborhood in St. Louis, Missouri * Patch, Gwbert, South Ceredigion, Wales People * Patch Adams, a.k.a. Hunter Adams (born 1945), founder of the Gesundheit! Institute * Alexander Patch (18 ...
. There was no lawsuit filed for this violation. In 2002,
MySQL AB MySQL AB was a Swedish software company founded in 1995. It was acquired by Sun Microsystems Sun Microsystems, Inc. (Sun for short) is a defunct American company that sold computers, computer components, software, and information technology ...
sued Progress NuSphere for copyright and trademark infringement in
United States district court#REDIRECT United States district court The United States district courts are the general trial court A trial court or court of first instance is a court A court is any person or institution, often as a government institution, with the aut ...
. NuSphere had allegedly violated MySQL's copyright by linking MySQL's GPL'ed code with NuSphere Gemini table without complying with the license. After a preliminary hearing before Judge Patti Saris on 27 February 2002, the parties entered settlement talks and eventually settled. After the hearing, FSF commented that "Judge Saris made clear that she sees the GNU GPL to be an enforceable and binding license." In August 2003, the
SCO Group SCO, The SCO Group, and The TSG Group are the various names of an American software company that became known for acquiring the Santa Cruz Operation's Server Software and Services divisions, and UnixWare and OpenServer technologies, and the ...
stated that they believed the GPL to have no legal validity and that they intended to pursue lawsuits over sections of code supposedly copied from SCO Unix into the
Linux kernel The Linux kernel is a free and open-source Free and open-source software (FOSS) is software that is both free software and open-source software where anyone is free software license, freely licensed to use, copy, study, and change the softwar ...
. This was a problematic stand for them, as they had distributed Linux and other GPL'ed code in their
Caldera OpenLinux Caldera OpenLinux (COL) is a defunct Linux distribution that was originally introduced by Caldera in 1997 based on the German LST Power Linux distribution, and then taken over and further developed by Caldera Systems (now SCO Group SCO ...
distribution, and there is little evidence that they had any legal right to do so except under the terms of the GPL. In February 2018, after federal circuit court judgement, appeal, and the case being (partially) remanded to the circuit court, the parties restated their remaining claims and provided a plan to move toward final judgement. The remaining claims revolved around
Project Monterey Project Monterey was an attempt to build a single Unix Unix (; trademarked as UNIX) is a family of Computer multitasking, multitasking, multiuser computer operating systems that derive from the original AT&T Corporation, AT&T Unix, whose deve ...
, and were finally settled in November 2021 by IBM paying $14.25 million to the TSG (previously SCO) bankruptcy trustee. In April 2004, the
netfilter Netfilter is a framework provided by the Linux kernel The Linux kernel is a free and open-source, Monolithic kernel, monolithic, Modular design, modular, Computer multitasking, multitasking, Unix-like operating system kernel (operating system) ...

netfilter
/
iptables iptables is a user-space A modern computer operating system An operating system (OS) is system software that manages computer hardware, computer software, software resources, and provides common daemon (computing), services for computer ...
project was granted a preliminary
injunction An injunction is a legal Law is a system of rules created and law enforcement, enforced through social or governmental institutions to regulate behavior,Robertson, ''Crimes against humanity'', 90. with its precise definition a matter of l ...
against Sitecom Germany by
Munich Munich ( ; german: München ; bar, Minga ) is the capital and most populous city of Bavaria. With a population of 1,558,395 inhabitants as of 31 July 2020, it is the List of cities in Germany by population, third-largest city in Germany, ...

Munich
District Court after Sitecom refused to desist from distributing Netfilter's GPL'ed software in violation of the terms of the GPL.
Harald Welte Harald Welte (1979), also known as LaForge, is a German programmer. Welte is the founder of the free software Free software (or libre software) is computer software Software is a collection of Instruction (computer science), instructio ...
, of Netfilter, was represented by
ifrOSS Institut für Rechtsfragen der Freien und Open Source Software, abbreviated to ifrOSS, (English: ''Institute for legal issues regarding free Free may refer to: Concept * Freedom, having the ability to act or change without constraint * Emancipat ...
co-founder Till Jaeger. In July 2004, the German court confirmed this injunction as a final ruling against Sitecom. The court's justification was that: :Defendant has infringed on the copyright of plaintiff by offering the software 'netfilter/iptables' for download and by advertising its distribution, without adhering to the license conditions of the GPL. Said actions would only be permissible if the defendant had a license grant.... This is independent of the questions whether the licensing conditions of the GPL have been effectively agreed upon between plaintiff and defendant or not. If the GPL were not agreed upon by the parties, defendant would notwithstanding lack the necessary rights to copy, distribute, and make the software 'netfilter/iptables' publicly available. This exactly mirrored the predictions given previously by the FSF's Eben Moglen. This ruling was important because it was the first time that a court had confirmed that violating terms of the GPL could be a copyright violation and established jurisprudence as to the enforceability of the GPL version 2 under German law. In May 2005, Daniel Wallace filed suit against the Free Software Foundation in the
Southern District of Indiana The United States District Court for the Southern District of Indiana (in case citations, S.D. Ind.) is a United States district courts, federal district court in Indiana. It was created in 1928 by an act of Congress of the United States, Congress ...
, contending that the GPL is an illegal attempt to fix prices (at zero). The suit was dismissed in March 2006, on the grounds that Wallace had failed to state a valid antitrust claim; the court noted that "the GPL encourages, rather than discourages, free competition and the distribution of computer operating systems, the benefits of which directly pass to consumers".Dismissal
of Wallace v. FSF. Fro
this article
on Groklaw.
Wallace was denied the possibility of further amending his complaint, and was ordered to pay the FSF's legal expenses. On 8 September 2005, the Seoul Central District Court ruled that the GPL was not material to a case dealing with
trade secret Trade secrets are a type of intellectual property that comprise formulas, best practice, practices, business process, processes, designs, legal instrument, instruments, patterns, or compilations of information that have inherent economic value be ...
s derived from GPL-licensed work. Defendants argued that since it is impossible to maintain trade secrets while being compliant with GPL and distributing the work, they are not in breach of trade secrets. This argument was considered without ground. On 6 September 2006, the gpl-violations.org project prevailed in court litigation against
D-Link D-Link Corporation () is a Taiwanese multinational networking equipment manufacturing corporation headquartered in Taipei Taipei (), officially Taipei City, is the capital and a special municipality of Taiwan (officially the Republic o ...
Germany GmbH regarding D-Link's copyright-infringing use of parts of the Linux kernel in storage devices they distributed. The judgment stated that the GPL is valid, legally binding, and stands in German court. In late 2007, the
BusyBox BusyBox is a software suite that provides several Unix utilities in a single executable file. It runs in a variety of POSIX The Portable Operating System Interface (POSIX) is a family of standardization, standards specified by the IEEE Comp ...
developers and the
Software Freedom Law Center The Software Freedom Law Center (SFLC) is an organization that provides '' pro bono'' legal representation and related services to not-for-profit developers of free software Free software (or libre software) is computer software Software ...
embarked upon a program to gain GPL compliance from distributors of BusyBox in
embedded system An embedded system is a computer system A computer is a machine that can be programmed to carry out Sequence, sequences of arithmetic or logical operations automatically. Modern computers can perform generic sets of operations known as Co ...
s, suing those who would not comply. These were claimed to be the first US uses of courts for enforcement of GPL obligations. (See BusyBox GPL lawsuits.) On 11 December 2008, the Free Software Foundation sued Cisco Systems, Inc. for copyright violations by its Linksys division, of the FSF's GPL-licensed
coreutils The GNU Core Utilities or coreutils is a package of GNU GNU () is an extensive collection of free software, which can be used as an operating system or can be used in parts with other operating systems. The use of the completed GNU tools led ...
, readline,
Parted GNU Parted (the name being the conjunction of the two words PARTition and EDitor) is a Free software, free partition editor, used for creating and deleting Partition (computing), partitions. This is useful for creating space for new operating system ...

Parted
,
Wget GNU Wget (or just Wget, formerly Geturl, also written as its package name, wget) is a computer program In imperative programming In computer science, imperative programming is a programming paradigm that uses Statement (computer science), state ...
,
GNU Compiler Collection The GNU Compiler Collection (GCC) is an optimizing compiler In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithm of an ...
,
binutils The GNU Binary Utilities, or , are a set of programming tools for creating and managing binary programs, object code, object files, libraries, profile data, and assembly code, assembly source code. Tools They were originally written by program ...
, and
GNU Debugger The GNU Debugger (GDB) is a Software portability, portable debugger that runs on many Unix-like systems and works for many programming languages, including Ada (programming language), Ada, C (programming language), C, C++, Objective-C, Free Pasc ...
software packages, which Linksys distributes in the Linux firmware of its
WRT54G The Linksys WRT54G Wi-Fi series is a series of Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area network A local area network (LAN) is a comput ...
wireless router A wireless router is a device that performs the functions of a Router (computing), router and also includes the functions of a wireless access point. It is used to provide access to the Internet or a Private network, private computer network. Dep ...

wireless router
s, as well as numerous other devices including DSL and Cable modems, Network Attached Storage devices, Voice-Over-IP gateways,
virtual private network A virtual private network (VPN) extends a private network In Internet networking, a private network is a computer network A computer network is a set of s sharing resources located on or provided by . The computers use common s over ...
devices, and a home theater/media player device. After six years of repeated complaints to
Cisco Cisco Systems, Inc. (Cisco) is an American multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational force, a military body from multiple countries * Multina ...
by the FSF, claims by Cisco that they would correct, or were correcting, their compliance problems (not providing complete copies of all source code and their modifications), of repeated new violations being discovered and reported with more products, and lack of action by Linksys (a process described on the FSF blog as a "five-years-running game of Whack-a-Mole") the FSF took them to court. Cisco settled the case six months later by agreeing "to appoint a Free Software Director for Linksys" to ensure compliance, "to notify previous recipients of Linksys products containing FSF programs of their rights under the GPL," to make source code of FSF programs freely available on its website, and to make a monetary contribution to the FSF. In 2011, it was noticed that GNU Emacs had been accidentally releasing some binaries without corresponding source code for two years, in opposition to the intended spirit of the
GPL The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software license A free-software license is a notice that grants the recipient of a piece of software extensive rights to modify and redistribute that ...
, resulting in a
copyright violation Copyright infringement (at times referred to as piracy) is the use of Copyright#Scope, works protected by copyright law without permission for a usage where such permission is required, thereby infringing certain exclusive rights granted to the ...
. Richard Stallman described this incident as a "very bad mistake", which was promptly fixed. The FSF did not sue any downstream redistributors who also unknowingly violated the GPL by distributing these binaries. In 2017 Artifex, the maker of
Ghostscript Ghostscript is a suite of software based on an interpreter for Adobe Systems Adobe Inc. ( ) is an American multinational computer software Software is a collection of Instruction (computer science), instructions and data (computing), dat ...

Ghostscript
, sued
HancomHancom (KOSDAQ: HAANSOFT) is an office suite software developer in South Korea. Established in 1990, the company created Hangul, a native word processing program for the Korean language. The story of Hancom mirrors the fortunes of Korea’s reborn s ...
, the maker of an office suite which included Ghostscript. Artifex offers two licenses for Ghostscript; one is the Affero GPL License and the other is a commercial license. Hancom did not acquire a commercial license from Artifex nor did it release its office suite as free software. Artifex sued Hancom in US District Court and made two claims. First, Hancom's use of Ghostscript was a violation of copyright; and second, Hancom's use of Ghostscript was a license violation. Judge Jacqueline Scott Corley found the GPL license was an enforceable contract and Hancom was in breach of contract.


Compatibility and multi-licensing

Code licensed under several other licenses can be combined with a program under the GPL without conflict, as long as the combination of restrictions on the work as a whole does not put any additional restrictions beyond what GPL allows. In addition to the regular terms of the GPL, there are additional restrictions and permissions one can apply: # If a user wants to combine code licensed under different versions of GPL, then this is only allowed if the code with the earlier GPL version includes an "or any later version" statement. For instance, the GPLv3-licensed GNU LibreDWG library cannot be used anymore by LibreCAD and FreeCAD who have GPLv2-only dependencies. # Code licensed under
LGPL The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...
is permitted to be linked with any other code no matter what license that code has, though the LGPL does add additional requirements for the combined work. LGPLv3 and GPLv2-only can thus commonly not be linked, as the combined Code work would add additional LGPLv3 requirements on top of the GPLv2-only licensed software. Code licensed under LGPLv2.x without the "any later version" statement can be Software relicensing, relicensed if the whole combined work is licensed to GPLv2 or GPLv3. FSF maintains a list of GPL-License compatibility, compatible free software licenses containing many of the most common free software licenses, such as the original MIT License, MIT/X license, the BSD license (in its current 3-clause form), and the Artistic License 2.0. Starting from GPLv3, it is unilaterally compatible for materials (like text and other media) under Creative Commons Attribution-ShareAlike 4.0 International License to be remixed into the GPL-licensed materials (prominently software), not vice versa, for niche use cases like game engine (GPL) with game scripts (CC BY-SA). David A. Wheeler has advocated that free/open source software developers use only GPL-compatible licenses, because doing otherwise makes it difficult for others to participate and contribute code. As a specific example of license incompatibility, Sun Microsystems' ZFS cannot be included in the GPL-licensed Linux kernel, because it is licensed under the GPL-incompatible Common Development and Distribution License. Furthermore, ZFS is protected by patents, so distributing an independently developed GPL-ed implementation would still require Oracle's permission. A number of businesses use multi-licensing to distribute a GPL version and sell a proprietary software, proprietary license to companies wishing to combine the package with proprietary code, using dynamic linking or not. Examples of such companies include
MySQL AB MySQL AB was a Swedish software company founded in 1995. It was acquired by Sun Microsystems Sun Microsystems, Inc. (Sun for short) is a defunct American company that sold computers, computer components, software, and information technology ...
, Digia PLC (Qt (framework), Qt framework, before 2011 from Nokia), Red Hat (Cygwin), and Riverbank Computing (PyQt). Other companies, like the Mozilla Foundation (products include Mozilla Application Suite, Mozilla Thunderbird, and Mozilla Firefox), used multi-licensing to distribute versions under the GPL and some other open-source licenses.


Text and other media

It is possible to use the GPL for text documents instead of computer programs, or more generally for all kinds of media, if it is clear what constitutes the source code (defined as "the preferred form of the work for making changes in it"). For manuals and textbooks, though, the FSF recommends the
GNU Free Documentation License The GNU Free Documentation License (GNU FDL or simply GFDL) is a copyleft Copyleft is the practice of granting the right to freely distribute and modify intellectual property with the requirement that the same rights be preserved in derivat ...
(GFDL) instead, which it created for this purpose. Nevertheless, the Debian developers recommended (in a resolution adopted in 2006) to license documentation for their project under the GPL, because of the incompatibility of the GFDL with the GPL (text licensed under the GFDL cannot be incorporated into GPL software).Debian Project
Resolution: Why the GNU Free Documentation License is not suitable for Debian
Voted February–March 2006. Retrieved 20 June 2009.
Also, the FLOSS Manuals foundation, an organization devoted to creating manuals for free software, decided to eschew the GFDL in favor of the GPL for its texts in 2007. If the GPL is used for computer fonts, any documents or images made with such fonts might also have to be distributed under the terms of the GPL. This is not the case in countries that recognize typefaces (the appearance of fonts) as being a useful article and thus Threshold of originality, not eligible for copyright, but font files as copyrighted computer software (which can complicate font embedding, since the document could be considered 'linked' to the font; in other words, embedding a vector font in a document could force it to be released under the GPL, but a rasterized rendering of the font would not be subject to the GPL). The FSF provides GPL font exception, an exception for cases where this is not desired.


Adoption

Historically, the GPL license family has been one of the most popular software licenses in the FOSS domain. A 1997 survey of Ibiblio, MetaLab, then the largest free software archive, showed that the GPL accounted for about half of the software licensed therein. Similarly, a 2000 survey of Red Hat Linux 7.1 found that 53% of the source code was licensed under the GPL. , about 68% of all projects and 82.1% of the open source industry certified licensed projects listed on SourceForge.net were from the GPL license family. , the GPL family accounted for 70.9% of the 44,927 free software projects listed on Freecode. After the release of the GPLv3 in June 2007, adoption of this new GPL version was much discussed and some projects decided against upgrading. For instance the Linux kernel, MySQL,
BusyBox BusyBox is a software suite that provides several Unix utilities in a single executable file. It runs in a variety of POSIX The Portable Operating System Interface (POSIX) is a family of standardization, standards specified by the IEEE Comp ...
, AdvFS, Blender (software), Blender, VLC media player, and MediaWiki decided against adopting GPLv3. On the other hand, in 2009, two years after the release of GPLv3, Google open-source programs office manager Chris DiBona reported that the number of open-source project licensed software that had moved from GPLv2 to GPLv3 was 50%, counting the projects hosted at Google Code. In 2011, four years after the release of the GPLv3, 6.5% of all open-source license projects are GPLv3 while 42.5% are GPLv2 according to Black Duck Software data. Following in 2011 ''451 Group'' analyst Matthew Aslett argued in a blog post that copyleft licenses went into decline and permissive licenses increased, based on statistics from Black Duck Software. Similarly, in February 2012 Jon Buys reported that among the top 50 projects on GitHub five projects were under a GPL license, including dual licensed and AGPL projects. GPL usage statistics from 2009 to 2013 was extracted from Freecode data by Walter van Holst while analyzing
license proliferation License proliferation is the phenomenon of an abundance of already existing and the continued creation of new software license A software license is a legal instrument (usually by way of contract law, with or without printed material) governin ...
.License proliferation: a naive quantitative analysis
on lwn.net "Walter van Holst is a legal consultant at the Dutch IT consulting company mitopics... Walter instead chose to use data from a software index, namely Freecode... Walter's 2009 data set consisted of 38,674 projects... The final column in the table shows the number of projects licensed under "any version of the GPL". In addition, Walter presented pie charts that showed the proportion of projects under various common-licenses. Notable in those data sets was that, whereas in 2009 the proportion of projects licensed GPLv2-only and GPLv3 was respectively 3% and 2%, by 2013, those numbers had risen to 7% and 5%."
In August 2013, according to Black Duck Software, the website's data shows that the GPL license family is used by 54% of open-source projects, with a breakdown of the individual licenses shown in the following table. However, a later study in 2013 showed that software licensed under the GPL license family has increased, and that even the data from Black Duck Software has shown a total increase of software projects licensed under GPL. The study used public information gathered from repositories of the Debian, Debian Project, and the study criticized Black Duck Software for not publishing their methodology used in collecting statistics. Daniel German, Professor in the Department of Computer Science at the University of Victoria in Canada, presented a talk in 2013 about the methodological challenges in determining which are the most widely used free software licenses, and showed how he could not replicate the result from Black Duck Software. In 2015, according to Black Duck, GPLv2 lost its first position to the MIT license and is now second, the GPLv3 dropped to fourth place while the Apache license kept its third position. A March 2015 analysis of the GitHub repositories revealed, for the GPL license family, a usage percentage of approximately 25% among licensed projects. In June 2016, an analysis of Fedora Project's packages revealed the GNU GPL version 2 or later as the most popular license, and the GNU GPL family as the most popular license family (followed by the MIT, BSD, and GNU LGPL families). An analysis of whitesourcesoftware.com in April 2018 of the FOSS ecosystem saw the GPLv3 on third place (18%) and the GPLv2 on fourth place (11%), after MIT license (26%) and Apache 2.0 license (21%).


Reception


Legal barrier to app stores

The GPL is incompatible with many application digital distribution systems, like the Mac App Store, and certain other software distribution platforms (on smartphones as well as PCs). The problem lies in the right "to make a copy for your neighbour", as this right is violated by digital rights management systems embedded within the platform to prevent copying of paid software. Even if the application is free in the app store in question, it might result in a violation of that app store's terms.The GPL, the App Store and You
on engadget.com (2011)
There is a distinction between an app ''store'', which sells
DRM DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement militaire ...
-restricted software under proprietary licenses, and the more general concept of digital distribution via some form of online software repository. Various UNIX-like Linux distribution, distributions provide app repositories, including Fedora (operating system), Fedora, RHEL, CentOS, Ubuntu (operating system), Ubuntu, Debian, FreeBSD, OpenBSD, and so on. These specific app repos all contain GPL-licensed software apps, in some cases even when the core project does not permit GPL-licensed code in the base system (for instance OpenBSD"Copyright Policy"
OpenBSD
). In other cases, such as the Ubuntu App Store, proprietary commercial software applications ''and'' GPL-licensed applications are both available via the same system; the reason that the Mac App Store (and similar projects) is incompatible with GPL-licensed apps is not inherent in the concept of an app store, but is rather specifically due to Apple's terms-of-use requirement that all apps in the store utilize Apple DRM restrictions. Ubuntu's app store does not demand any such requirement: "These terms do not limit or restrict your rights under any applicable open source software licenses."


Microsoft

In 2001,
Microsoft Microsoft Corporation is an American multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational force, a military body from multiple countries * Multination ...

Microsoft
CEO Steve Ballmer referred to Linux as "a cancer that attaches itself in an intellectual property sense to everything it touches". In response to Microsoft's attacks on the GPL, several prominent Free Software developers and advocates released a joint statement supporting the license. Microsoft has released Microsoft Windows Services for UNIX, which contains GPL-licensed code. In July 2009, Microsoft itself released a body of around 20,000 lines of Linux driver code under the GPL. The Hyper-V code that is part of the submitted code used open-source components licensed under the GPL and was originally statically linked to proprietary binary parts, the latter being inadmissible in GPL-licensed software.


"Viral" nature

The description of the GPL as Viral license, "viral", when called 'General Public Virus' or 'GNU Public Virus' (GPV), dates back to a year after the GPLv1 was released. In 2001, the term received broader public attention when Craig Mundie, Microsoft Senior Vice President, described the GPL as being "viral". Mundie argues that the GPL has a "viral" effect in that it only allows the conveyance of whole programs, which means programs that GPL linking exception, link to GPL libraries must themselves be under a GPL-compatible license, else they cannot be combined and distributed. In 2006, Richard Stallman responded in an interview that Mundie's metaphor of a "virus" is wrong as software under the GPL does not "attack" or "infect" other software. Accordingly, Stallman believes that comparing the GPL to a virus is inappropriate, and that a better metaphor for software under the GPL would be a Chlorophytum comosum, spider plant: if one takes a piece of it and puts it somewhere else, it grows there too. On the other hand, the concept of a viral nature of the GPL was taken up by others later too. For instance, a 2008 article stated: "The GPL license is 'viral,' meaning any derivative work you create containing even the smallest portion of the previously GPL licensed software must also be licensed under the GPL license."


Barrier to commercialization

The FreeBSD project has stated that "a less publicized and unintended use of the GPL is that it is very favorable to large companies that want to undercut software companies. In other words, the GPL is well suited for use as a marketing weapon, potentially reducing overall economic benefit and contributing to monopolistic behavior" and that the GPL can "present a real problem for those wishing to commercialize and profit from software." Richard Stallman wrote about the practice of selling license exceptions to free software licenses as an example of ethically acceptable commercialization practice. Selling exceptions here means that the copyright holder of a given software releases it (along with the corresponding source code) to the public under a free software license, "then lets customers pay for permission to use the same code under different terms, for instance allowing its inclusion in proprietary applications". Stallman considered selling exceptions "acceptable since the 1990s, and on occasion I've suggested it to companies. Sometimes this approach has made it possible for important programs to become free software". Although the FSF does not practice selling exceptions, a comparison with the X11 license (which is a non-copyleft free software license) is proposed for suggesting that this commercialization technique should be regarded as ethically acceptable. Releasing a given program under a non-copyleft free software license would permit embedding the code in proprietary software. Stallman comments that "either we have to conclude that it's wrong to release anything under the X11 license—a conclusion I find unacceptably extreme—or reject this implication. Using a non-copyleft license is weak, and usually an inferior choice, but it's not wrong. In other words, selling exceptions permits some embedding in proprietary software, and the X11 license permits even more embedding. If this doesn't make the X11 license unacceptable, it doesn't make selling exceptions unacceptable".


Open-source criticism

In 2000, developer and author Nikolai Bezroukov published an analysis and comprehensive critique of GPL's foundations and Stallman's software development model, called "Labyrinth of Software Freedom". Version 2 of the WTFPL (Do What The Fuck You Want To Public License) was created by Debian project leader Sam Hocevar in 2004 as a parody of the GPL. In 2005, open source software advocate Eric S. Raymond questioned the relevance of GPL then for the FOSS ecosystem, stating: "We don't need the GPL anymore. It's based on the belief that open source software is weak and needs to be protected. Open source would be succeeding faster if the GPL didn't make lots of people nervous about adopting it." Richard Stallman replied: "GPL is designed to ... ensure that every user of a program gets the essential freedoms—to run it, to study and change the source code, to redistribute copies, and to publish modified versions... [Raymond] addresses the issue in terms of different goals and values—those of 'open source,' which do not include defending software users' freedom to share and change software." In 2007,
Allison Randal Allison Randal is a software developer and author. She was the chief architect of the Parrot virtual machine, a member of the board of directors for The Perl Foundation, a director of the Python Software Foundation from 2010 to 2012, and the ...

Allison Randal
, who took part in the GPL draft committee, criticized the GPLv3 for being License compatibility, incompatible with the GPLv2 and for missing clarity in the formulation. Similarly, Whurley prophesied in 2007 the downfall of the GPL due to the lack of focus for the developers with GPLv3 which would drive them towards permissive licenses. In 2009, David Chisnall described in an InformIT (publisher), InformIT article, "The Failure of the GPL", the problems with the GPL, among them incompatibility and complexity of the license text. In 2014, dtrace developer and Joyent Chief Technical Officer, CTO Bryan Cantrill called the copyleft GPL a "Corporate Open Source Anti-pattern" by being "anti-collaborative" and recommended instead Permissive license, permissive software licenses.


GPLv3 criticism

Already in September 2006, in the draft process of the GPLv3, several high-profile developers of the Linux kernel, for instance Linus Torvalds,
Greg Kroah-Hartman Greg Kroah-Hartman (GKH) is a major Linux kernel The Linux kernel is a free and open-source Free and open-source software (FOSS) is software Software is a collection of Instruction (computer science), instructions and data (computing), ...
, and , warned on a splitting of the FOSS community: "the release of GPLv3 portends the
Balkanisation Balkanization refers to the fragmentation, or sub-fragmentation, of a larger region or state into smaller regions or states, which may be hostile or uncooperative with one another. When sponsored or encouraged by a sovereign third party, the term ...
of the entire Open Source Universe upon which we rely." Similarly Benjamin Mako Hill argued in 2006 on the GPLv3 draft, noting that a united, collaborating community is more important than a single license. Following the GPLv3 release in 2007, some journalists and
Toybox Toybox is a free and open-source software Free and open-source software (FOSS) is software Software is a collection of Instruction (computer science), instructions and data (computing), data that tell a computer how to work. This is in con ...
developer Rob Landley criticized that with the introduction of the GPLv3 the split between the open source and free software community became wider than ever. As the significantly extended GPLv3 is essentially incompatible with the GPLv2, compatibility between both is only given under the optional "or later" clause of the GPL, which was not taken for instance by the Linux kernel. Bruce Byfield noted that before the release of the GPLv3, the GPLv2 was a unifying element between the open-source and the free software community. For the LGPLv3, GNU TLS maintainer Nikos Mavrogiannopoulos similarly argued, "If we assume that its [the LGPLv3] primary goal is to be used by free software, then it blatantly fails that", after he re-licensed ''GNU TLS'' from LGPLv3 back to LGPLv2.1 due to license compatibility issues. Lawrence Rosen, attorney and computer specialist, praised in 2007 how the community using the Apache license was now able to work together with the GPL community in a compatible manner, as the problems of GPLv2 compatibility with Apache licensed software were resolved with the GPLv3. He said, "I predict that one of the biggest success stories of GPLv3 will be the realization that the entire universe of free and open-source software can thus be combined into comprehensive open source solutions for customers worldwide." In July 2013, Flask (web framework), Flask developer Armin Ronacher draws a less optimistic conclusion on the GPL compatibility in the FOSS ecosystem: "When the GPL is involved the complexities of licensing becomes a non fun version of a riddle", also noting that the conflict between Apache License 2.0 and GPLv2 still has impact on the ecosystem.


See also

* Anti-copyright * Dual-licensing * European Union Public Licence (EUPL) * GPL font exception * GPL linking exception * List of software licenses * Permissive and copyleft licenses * :Software using the GPL license


Notes


References


External links


GNU General Public License
(version 3)
GNU General Public License v2.0
This version is deprecation, deprecated by the FSF but is still used by many software projects, including
Linux kernel The Linux kernel is a free and open-source Free and open-source software (FOSS) is software that is both free software and open-source software where anyone is free software license, freely licensed to use, copy, study, and change the softwar ...
and GNU packages.
GNU General Public License v1.0
This version is deprecation, deprecated by the FSF.
The Emacs General Public License
a February 1988 version, a direct predecessor of the GNU GPL
History of the GPL
by Li-Cheng Tai, 4 July 2001

(Covers GPLv2 and v3)—from the
Software Freedom Law Center The Software Freedom Law Center (SFLC) is an organization that provides '' pro bono'' legal representation and related services to not-for-profit developers of free software Free software (or libre software) is computer software Software ...

A paper on enforcing the GPL




edited by Robert Chassell
List of presentation transcripts about the GPL and free software licenses
by the FSFE
The Labyrinth of Software Freedom
BSD vs GPL and social aspects of free licensing debate, by Nikolai Bezroukov {{FOSS Free and open-source software licenses Copyleft software licenses GNU Project Copyleft