![Copyleft](https://upload.wikimedia.org/wikipedia/commons/8/8b/Copyleft.svg)
Copyleft is the legal technique of granting certain freedoms over copies of
copyright
A copyright is a type of intellectual property that gives its owner the exclusive right to copy, distribute, adapt, display, and perform a creative work, usually for a limited time. The creative work may be in a literary, artistic, education ...
ed works with the requirement that the same rights be preserved in
derivative work
In copyright law, a derivative work is an expressive creation that includes major copyrightable elements of an original, previously created first work (the underlying work). The derivative work becomes a second, separate work independent in fo ...
s. In this sense, ''freedoms'' refers to the use of the work for any purpose, and the ability to modify, copy, share, and redistribute the work, with or without a fee.
License
A license (or licence) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit).
A license is granted by a party (licensor) to another party (licensee) as an element of an agreeme ...
s which implement copyleft can be used to maintain copyright conditions for works ranging from
computer software
Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work.
At the lowest programming level, executable code consists ...
, to
documents
A document is a writing, written, drawing, drawn, presented, or memorialized representation of thought, often the manifestation of nonfiction, non-fictional, as well as fictional, content. The word originates from the Latin ''Documentum'', w ...
,
art
Art is a diverse range of human activity, and resulting product, that involves creative or imaginative talent expressive of technical proficiency, beauty, emotional power, or conceptual ideas.
There is no generally agreed definition of wha ...
, scientific discoveries and even
certain patents.
Copyleft
software license
A software license is a legal instrument (usually by way of contract law, with or without printed material) governing the use or redistribution of software. Under United States copyright law, all software is copyright protected, in both source ...
s are considered ''protective'' or ''reciprocal'' in contrast with
permissive {{about, , the 1970 British film, Permissive (film), the grammatical mode, Permissive mood, the flavor of software license, permissive free software licence
A permissive cell or host is one that allows a virus to circumvent its defenses and replica ...
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 versions. Free software is a matter of liberty, no ...
licenses,
and require that information necessary for reproducing and modifying the work must be made available to recipients of the software program, which are often distributed as
binary executables
In computing, executable code, an executable file, or an executable program, sometimes simply referred to as an executable or binary, causes a computer "to perform indicated tasks according to encoded instructions", as opposed to a data file ...
. This information is most commonly in the form of
source code
In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the wo ...
files, which usually contain a copy of the license terms and acknowledge the authors of the code.
Notable copyleft licenses include the
GNU General Public License
The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the Four Freedoms (Free software), four freedoms to run, study, share, and modify the software. The license was th ...
(GPL), originally 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. He campaigns for software to be distributed in such a manner that its users have the freedom to ...
, which was the first software copyleft license to see extensive use, the
Mozilla Public License
The Mozilla Public License (MPL) is a free and open-source weak copyleft license for most Mozilla Foundation software such as Firefox and Thunderbird The MPL license is developed and maintained by Mozilla, which seeks to balance the concerns ...
, the
Free Art License
The Free Art License (FAL), (french: Licence Art Libre (LAL)) is a copyleft license that grants the right to freely copy, distribute, and transform creative works.
History
The license was written in July 2000 with contributions from the mailin ...
, and the
Creative Commons
Creative Commons (CC) is an American non-profit organization and international network devoted to educational access and expanding the range of creative works available for others to build upon legally and to share. The organization has release ...
share-alike
Share-alike (🄎) is a copyright licensing term, originally used by the Creative Commons project, to describe works or licenses that require copies or adaptations of the work to be released under the same or similar license as the original. Copy ...
license condition,
with the last two being intended for other types of works, such as documents and pictures, both academic or artistic in nature.
History
An early use of the word ''copyleft'' was in
Li-Chen Wang
Li-Chen Wang (born 1935) is an American computer engineer, best known for his ''Palo Alto Tiny BASIC'' for Intel 8080-based microcomputers. He was a member of the Homebrew Computer Club and made significant contributions to the software for early ...
's Palo Alto
Tiny BASIC
Tiny BASIC is a family of dialects of the BASIC programming language that can fit into 4 or fewer KBs of memory. Tiny BASIC was designed in response to the open letter published by Bill Gates complaining about users pirating Altair BASIC, which ...
's distribution notice "@COPYLEFT ALL WRONGS RESERVED" in June 1976. Tiny BASIC was not distributed under any formal form of copyleft distribution terms, but it was presented in a context where source code was being shared and modified. In fact, Wang had earlier contributed edits to Tiny BASIC Extended before writing his own
BASIC interpreter
A BASIC interpreter is an interpreter that enables users to enter and run programs in the BASIC language and was, for the first part of the microcomputer era, the default application that computers would launch. Users were expected to use the BAS ...
. He encouraged others to adapt his source code and publish their adaptions, as with Roger Rauskolb's version of PATB published in ''
Interface Age
''Interface Age'', "published for the home computerist", was a computer magazine aimed at the early microcomputer and home computer market. Its first issue was published in August 1976 and the last one in September 1984. It had a technical focus ...
''.
The concept of copyleft was described in
Richard Stallman
Richard Matthew Stallman (; born March 16, 1953), also known by his initials, rms, is an American free software movement activist and programmer. He campaigns for software to be distributed in such a manner that its users have the freedom to ...
's ''
GNU Manifesto
__NOTOC__
The ''GNU Manifesto'' is a call-to-action by Richard Stallman encouraging participation and support of the GNU Project's goal in developing the GNU free computer operating system. The GNU Manifesto was published in March 1985 in '' D ...
'' in 1985, where he wrote:
GNU is not in the public domain. Everyone will be permitted to modify and redistribute GNU, but no distributor will be allowed to restrict its further redistribution. That is to say, proprietary modifications will not be allowed. I want to make sure that all versions of GNU remain free.
Stallman worked a few years earlier on a
Lisp
A lisp is a speech impairment in which a person misarticulates sibilants (, , , , , , , ). These misarticulations often result in unclear speech.
Types
* A frontal lisp occurs when the tongue is placed anterior to the target. Interdental lisping ...
interpreter.
Symbolics
Symbolics was a computer manufacturer Symbolics, Inc., and a privately held company that acquired the assets of the former company and continues to sell and maintain the Open Genera Lisp system and the Macsyma computer algebra system. asked to use the Lisp interpreter, and Stallman agreed to supply them with a
public domain
The public domain (PD) consists of all the creative work
A creative work is a manifestation of creative effort including fine artwork (sculpture, paintings, drawing, sketching, performance art), dance, writing (literature), filmmaking, ...
version of his work. Symbolics extended and improved the Lisp interpreter, but when Stallman wanted access to the improvements that Symbolics had made to his interpreter, Symbolics refused. Stallman then, in 1984, proceeded to work towards eradicating this emerging behavior and culture of
proprietary software
Proprietary software is software that is deemed within the free and open-source software to be non-free because its creator, publisher, or other rightsholder or rightsholder partner exercises a legal monopoly afforded by modern copyright and int ...
, which he named ''software hoarding''. This was not the first time Stallman had dealt with proprietary software, but he deemed this interaction a "turning point". He justified software sharing, protesting that when sharing, the software online can be copied without the loss of the original piece of work. The software can be used multiple times without ever being damaged or worn out.
As Stallman deemed it impractical in the short term to eliminate current copyright law and the wrongs he perceived it to perpetuate, he decided to work within the framework of existing
law
Law is a set of rules that are created and are enforceable by social or governmental institutions to regulate behavior,Robertson, ''Crimes against humanity'', 90. with its precise definition a matter of longstanding debate. It has been vario ...
; in 1985, he created his own copyright license, the Emacs General Public License, the first copyleft license. This later evolved into the
GNU General Public License
The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the Four Freedoms (Free software), four freedoms to run, study, share, and modify the software. The license was th ...
, which is now one of the most popular free-software licenses. For the first time, a copyright holder had taken steps to ensure that the maximal number of rights be perpetually transferred to a program's users, no matter what subsequent revisions anyone made to the original program. This original GPL did not grant rights to the public at large, only those who had already received the program; but it was the best that could be done under existing law.
The new license was not at this time given the copyleft label.
Richard Stallman stated that the use of "Copyleft" comes from
Don Hopkins
Don Hopkins is an artist and programmer specializing in human computer interaction and computer graphics. He is an alumnus of the University of Maryland, College Park, University of Maryland and a former member of the University of Maryland Huma ...
, who mailed him a letter in 1984 or 1985, on which was written: "Copyleft – all rights reversed".
In the early 1970s, the self-published book ''
Principia Discordia
The ''Principia Discordia'' is the first published Discordian religious text. It was written by Greg Hill (Malaclypse the Younger) with Kerry Wendell Thornley (Lord Omar Khayyam Ravenhurst) and others. The first edition was printed allegedly using ...
'' contains the notice "Ⓚ – reprint what you like" (''
sic
The Latin adverb ''sic'' (; "thus", "just as"; in full: , "thus was it written") inserted after a quoted word or passage indicates that the quoted matter has been transcribed or translated exactly as found in the source text, complete with any e ...
''). In the arts,
Ray Johnson
Raymond Edward "Ray" Johnson (October 16, 1927 – January 13, 1995) was an American artist. Known primarily as a collagist and correspondence artist, he was a seminal figure in the history of Neo-Dada and early Pop art and was described as had earlier coined the term independently as it pertained to his making of and distribution of his mixed media imagery in his
mail art
Mail art, also known as postal art and correspondence art, is an artistic movement centered on sending small-scale works through the postal service. It initially developed out of what eventually became Ray Johnson's New York Correspondence Schoo ...
and ephemeral gifts, for which he encouraged the making of
derivative work
In copyright law, a derivative work is an expressive creation that includes major copyrightable elements of an original, previously created first work (the underlying work). The derivative work becomes a second, separate work independent in fo ...
s. (While the phrase appears briefly as (or on) one of his pieces in the 2002 documentary ''
How to Draw a Bunny'', Johnson himself is not referenced in the 2001 documentary ''
Revolution OS
''Revolution OS'' is a 2001 documentary film that traces the twenty-year history of GNU, Linux, open source, and the free software movement.
Directed by J. T. S. Moore, the film features interviews with prominent hackers and entrepreneurs incl ...
''.)
In
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
, a series of meetings taking place in 2000 under the title "Copyleft Attitude" gave birth to the
Free Art License
The Free Art License (FAL), (french: Licence Art Libre (LAL)) is a copyleft license that grants the right to freely copy, distribute, and transform creative works.
History
The license was written in July 2000 with contributions from the mailin ...
(FAL), theoretically valid in any jurisdiction bound by the
Berne Convention
The Berne Convention for the Protection of Literary and Artistic Works, usually known as the Berne Convention, was an international assembly held in 1886 in the Swiss city of Bern by ten European countries with the goal to agree on a set of leg ...
and recommended by Stallman's own
Free Software Foundation
The Free Software Foundation (FSF) is a 501(c)#501(c)(3), 501(c)(3) non-profit organization founded by Richard Stallman on October 4, 1985, to support the free software movement, with the organization's preference for software being distributed ...
. Shortly thereafter, a separate, unrelated initiative in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
yielded the
Creative Commons license
A Creative Commons (CC) license is one of several public copyright licenses that enable the free distribution of an otherwise copyrighted "work".A "work" is any creative material made by a person. A painting, a graphic, a book, a song/lyrics ...
, available since 2001 in several different versions (only some of which can be described as copyleft) and more specifically tailored to U.S. law.
Copyleft principles
Freedom
While copyright law gives software authors control over copying, distribution and modification of their works, the goal of copyleft is to give all users of the work the freedom to carry out all of these activities. These freedoms (from the
Free Software Definition
The Free Software Definition written by Richard Stallman and published by the Free Software Foundation (FSF), defines free software as being software that ensures that the end users have freedom in using, studying, sharing and modifying that softwa ...
) include:
;Freedom 0
:the freedom to use the work
;Freedom 1
:the freedom to study the work
;Freedom 2
:the freedom to copy and share the work with others
;Freedom 3
:the freedom to modify the work, and the freedom to distribute modified and therefore derivative works
Similar terms are present in the
Open Source Definition
''The Open Source Definition'' is a document published by the Open Source Initiative, to determine whether a software license can be labeled with the open-source certification mark.
The definition was taken from the exact text of the Debian Free ...
, a separate definition that contains similar freedoms. The vast majority of copyleft licenses satisfy both definitions, that of the Free Software Definition and Open Source Definition.
By guaranteeing viewers and users of a work the freedom and permission to reproduce,
adapt
ADAPT (formerly American Disabled for Attendant Programs Today) is a United States grassroots disability rights organization with chapters in 30 states and Washington, D.C. They use nonviolent direct action in order to bring about disability just ...
, or distribute it, copyleft licenses are distinct from other types of copyright licenses that limit such freedoms.
Reciprocity
Instead of allowing a work to fall completely into the
public domain
The public domain (PD) consists of all the creative work
A creative work is a manifestation of creative effort including fine artwork (sculpture, paintings, drawing, sketching, performance art), dance, writing (literature), filmmaking, ...
, where no ownership of copyright is claimed, copyleft allows authors to impose restrictions on the use of their work. One of the main restrictions imposed by copyleft is that
derived works must also be released under a compatible copyleft license.
This is due to the underlying principle of copyleft: that anyone can benefit freely from the previous work of others, but that any modifications to that work should benefit everyone else as well, and thus must be released under similar terms. For this reason, copyleft licenses are also known as
reciprocal
Reciprocal may refer to:
In mathematics
* Multiplicative inverse, in mathematics, the number 1/''x'', which multiplied by ''x'' gives the product 1, also known as a ''reciprocal''
* Reciprocal polynomial, a polynomial obtained from another pol ...
licenses: any modifiers of a copyleft-licensed work are expected to reciprocate the author's action of copyleft-licensing the software by also copyleft-licensing any derivatives they might have made. Because of this requirement, copyleft licenses have also been described as "viral" due to their self-perpetuating terms.
In addition to restrictions on copying, copyleft licenses address other possible impediments. They ensure that rights cannot be later
revoke
In trick-taking card games, a revoke (or renege, or ) is a violation of the rules regarding the play of tricks serious enough to render the round invalid. A revoke is a violation ranked in seriousness somewhat below overt cheating, and is cons ...
d, and require the work and its derivatives to be provided in a form that allows further modifications to be made. In
software
Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work.
At the lowest programming level, executable code consists ...
, this means requiring that the
source code
In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the wo ...
of the derived work be made available together with the software itself.
Economic incentive
The economic incentives to work on copyleft content can vary. Traditional copyright law is designed to promote progress by providing economic benefits to creators. When choosing to copyleft their work, content creators may seek complementary benefits like recognition from their peers.
In the world of computer programming, copyleft-licensed computer programs are often created by programmers to fill a need they have noticed. Such programs are often published with a copyleft license simply to ensure that subsequent users can also freely use modified versions of that program. This is especially true for creators who wish to prevent "open source hijacking", or the act of reusing open-source code and then adding extra restrictions to it, an action prevented by copyleft-licensing the software. Some creators, such as
Elastic
Elastic is a word often used to describe or identify certain types of elastomer, elastic used in garments or stretchable fabrics.
Elastic may also refer to:
Alternative name
* Rubber band, ring-shaped band of rubber used to hold objects togeth ...
, feel that preventing
commercial
Commercial may refer to:
* a dose of advertising conveyed through media (such as - for example - radio or television)
** Radio advertisement
** Television advertisement
* (adjective for:) commerce, a system of voluntary exchange of products and s ...
enterprises from using and then selling their product under a proprietary license is also an incentive.
Furthermore, the
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. The open-source model is a decentralized sof ...
culture of programming has been described as a gift culture, where social power is determined by an individual's contributions. Contributing to or creating open-source, copyleft-licensed software of high quality can lead to contributors gaining valuable experience and can lead to future career opportunities.
Copyleft software has economic effects beyond individual creators. The presence of quality copyleft software can force proprietary software developers to increase the quality of their software to compete with free software. This may also have the effect of preventing monopolies in areas dominated by proprietary software. However, competition with proprietary software can also be a reason to forgo copyleft. The
Free Software Foundation
The Free Software Foundation (FSF) is a 501(c)#501(c)(3), 501(c)(3) non-profit organization founded by Richard Stallman on October 4, 1985, to support the free software movement, with the organization's preference for software being distributed ...
recommends that when "widespread use of the code is vital for advancing the cause of free software", allowing the code to be copied and used freely is more important than a copyleft.
Copyleft application
Common practice for using copyleft is to codify the copying terms for a work with a
license
A license (or licence) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit).
A license is granted by a party (licensor) to another party (licensee) as an element of an agreeme ...
. Any such license typically includes all the provisions and principles of copyleft inside the license's terms. This includes the freedom to use the work, study the work, copy and share the work with others, modify the work, and distribute exact or modified versions of that work, with or without a fee.
Unlike similar permissive licenses that also grant these freedoms, copyleft licenses also ensure that any modified versions of a work covered by a copyleft license must also grant these freedoms. Thus, copyleft licenses have conditions: that modifications of any work licensed under a copyleft license must be distributed under a compatible copyleft scheme and that the distributed modified work must include a means of modifying the work. Under
fair use
Fair use is a doctrine in United States law 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 interests ...
, however, copyleft licenses may be superseded, just like regular copyrights. Therefore, any person utilizing a source licensed under a copyleft license for works they invent is free to choose any other license (or none at all) provided they meet the fair use standard.
Copyleft licenses necessarily make creative use of relevant rules and laws to enforce their provisions. For example, when using copyright law, those who contribute to a work under copyleft usually must gain, defer, or assign copyright holder status. By submitting the copyright of their contributions under a copyleft license, they deliberately give up some of the rights that normally follow from copyright, including the right to be the unique distributor of copies of the work.
Some laws used for copyleft licenses vary from one country to another, and may also be granted in terms that vary from country to country. For example, in some countries, it is acceptable to sell a software product without warranty, in standard
GNU General Public License
The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the Four Freedoms (Free software), four freedoms to run, study, share, and modify the software. The license was th ...
style, while in most
European countries
The list below includes all entities falling even partially under any of the various common definitions of Europe, geographical or political. Fifty generally recognised sovereign states, Kosovo with limited, but substantial, international reco ...
it is not permitted for a software distributor to
waive
A waiver is the voluntary relinquishment or surrender of some known right or privilege.
Regulatory agencies of state departments or the federal government may issue waivers to exempt companies from certain regulations. For example, a United St ...
all warranties regarding a sold product. For this reason, the extent of such warranties is specified in most European copyleft licenses, for example, the
European Union Public Licence
The European Union Public Licence (EUPL) is a free software licence that was written and approved by the European Commission. The licence is available in 23 official languages of the European Union. All linguistic versions have the same validity. ...
(EUPL), or the
CeCILL license, a license that allows one to use GNU GPL in combination with a limited warranty.
For projects which will be run over a network, a variation of the GNU GPL, called 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 Pu ...
(GNU AGPL), ensures that the source code is available to users of software over a network.
Types and relation to other licenses
![Cc-sa](https://upload.wikimedia.org/wikipedia/commons/2/29/Cc-sa.svg)
Copyleft is a distinguishing feature of some
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 versions. Free software is a matter of liberty, no ...
licenses, while other
free-software licenses are not copyleft licenses because they do not require the licensee to distribute derivative works under the same license. There is an ongoing debate as to which class of license provides the greater degree of freedom. This debate hinges on complex issues, such as the definition of freedom and whose freedoms are more important: the potential future recipients of a work (freedom from proprietization) or just the initial recipient (freedom to proprietize). However, current copyright law and the availability of both types of licenses, copyleft and permissive, allow authors to choose the type under which to license the works they invent.
For documents, art, and other works other than software and code, the
Creative Commons
Creative Commons (CC) is an American non-profit organization and international network devoted to educational access and expanding the range of creative works available for others to build upon legally and to share. The organization has release ...
share-alike licensing system and the
GNU Free Documentation License
The GNU Free Documentation License (GNU FDL or simply GFDL) is a copyleft license for free documentation, designed by the Free Software Foundation (FSF) for the GNU Project. It is similar to the GNU General Public License, giving readers the r ...
(GFDL) allow authors to apply limitations to certain sections of their work, exempting some parts of the work from the full copyleft mechanism. In the case of the GFDL, these limitations include the use of invariant sections, which may not be altered by future editors. The initial intention of the GFDL was as a device for supporting the
documentation
Documentation is any communicable material that is used to describe, explain or instruct regarding some attributes of an object, system or procedure, such as its parts, assembly, installation, maintenance and use. As a form of knowledge manageme ...
of copylefted software. However, the result is that it can be used for any kind of document.
Strong and weak copyleft
The strength of the copyleft license governing a work is determined by the extent to its provisions can be imposed on all kinds of derivative works. Thus, the term "weak copyleft" refers to licenses where not all derivative works inherit the copyleft license; whether a derivative work inherits or not often depends on how it was derived.
"Weak copyleft" licenses are often used to cover
software libraries
In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and subro ...
. This allows other software to link to the library and be redistributed without the requirement for the linking software to also be licensed under the same terms. Only changes to the software licensed under a "weak copyleft" license become subject itself to copyleft provisions of such a license. This allows programs of any license to be compiled and linked against copylefted libraries such as
glibc
The GNU C Library, commonly known as glibc, is the GNU Project's implementation of the C standard library. Despite its name, it now also directly supports C++ (and, indirectly, other programming languages). It was started in the 1980s by ...
and then redistributed without any re-licensing required. The concrete effect of strong vs. weak copyleft has yet to be tested in court. Free-software licenses that use "weak" copyleft 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 ...
and the
Mozilla Public License
The Mozilla Public License (MPL) is a free and open-source weak copyleft license for most Mozilla Foundation software such as Firefox and Thunderbird The MPL license is developed and maintained by Mozilla, which seeks to balance the concerns ...
.
The
GNU General Public License
The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the Four Freedoms (Free software), four freedoms to run, study, share, and modify the software. The license was th ...
is an example of a license implementing strong copyleft. A stronger copyleft license is the
AGPL, which requires the publishing of the source code for
software as a service
Software as a service (SaaS ) is a software licensing and delivery model in which software is licensed on a subscription basis and is centrally hosted. SaaS is also known as "on-demand software" and Web-based/Web-hosted software.
SaaS is con ...
use cases.
[List of free-software licences on the GNU website](_blank)
"''We recommend that developers consider using the GNU AGPL for any software which will commonly be run over a network''".
The
Sybase Open Watcom Public License
The Sybase Open Watcom Public Licence is a software license that has been approved by the Open Source Initiative. It is the licence under which the Open Watcom C/C++ compiler is released.
The license has not been accepted as "free" under the Deb ...
is one of the strongest copyleft licenses, as this license closes the so-called "private usage" loophole of the GPL, and requires the publishing of source code in any use case. For this reason, the license is considered non-free by the
Free Software Foundation
The Free Software Foundation (FSF) is a 501(c)#501(c)(3), 501(c)(3) non-profit organization founded by Richard Stallman on October 4, 1985, to support the free software movement, with the organization's preference for software being distributed ...
, the
GNU Project
The GNU Project () is a free software, mass collaboration project announced by Richard Stallman on September 27, 1983. Its goal is to give computer users freedom and control in their use of their computers and computing devices by collaborati ...
, and the
Debian
Debian (), also known as Debian GNU/Linux, is a Linux distribution composed of free and open-source software, developed by the community-supported Debian Project, which was established by Ian Murdock on August 16, 1993. The first version of D ...
project.
However, the license is accepted as
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. The open-source model is a decentralized sof ...
by the
OSI
OSI may refer to:
Places
* Osijek Airport (IATA code: OSI), an airport in Croatia
* Ősi, a village in Veszprém county, Hungary
* Oši, an archaeological site in Semigallia, Latvia
* Osi, a village in Ido-Osi, Ekiti State, Nigeria
* Osi, Ekiti ...
.
The
Design Science License (DSL) is a strong copyleft license that applies to any work, not only software or documentation, but also literature, artworks, music, photography, and video. DSL was written by Michael Stutz after he took an interest in applying GNU-style copyleft to non-software works, which later came to be called
libre works. In the 1990s, it was used on music recordings, visual art, and even novels. It is not considered compatible with the GNU GPL by the Free Software Foundation.
Full and partial copyleft
"Full" and "partial" copyleft relate to another issue. Full copyleft exists when all parts of a work (except the license itself) may only be modified and distributed under the terms of the work's copyleft license. Partial copyleft, by contrast, exempts some parts of the work from the copyleft provisions, permitting distribution of some modifications under terms other than the copyleft license, or in some other way does not impose all the principles of copylefting on the work. An example of partial copyleft is the GPL linking exception made for some software packages.
Share-alike
The "
share-alike
Share-alike (🄎) is a copyright licensing term, originally used by the Creative Commons project, to describe works or licenses that require copies or adaptations of the work to be released under the same or similar license as the original. Copy ...
" condition in some licenses imposes the requirement that any freedom that is granted regarding the original work must be granted on exactly the same or compatible terms in any derived work.
This implies that any copyleft license is automatically a share-alike license but not the other way around, as some share-alike licenses include further restrictions such as prohibiting commercial use. Another restriction is that not everyone wants to share their work and some share-alike agreements require that the whole body of work be shared, even if the author only wants to share a certain part. The plus side for an author of source code is that any modification to the code will not only benefit the original author but that the author will be recognized and ensure the same or compatible license terms cover the changed code. Some Creative Commons licenses are examples of share-alike copyleft licenses.
Permissive licenses
Permissive software licenses are those that grant users of the software the same freedoms as copyleft licenses but do not require modified versions of that software to also include those freedoms. They have minimal restrictions on how the software can be used, modified, and redistributed, and are thus not copyleft licenses. Examples of this type of license include the
X11 license
The MIT License is a permissive free software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts only very limited restriction on reuse and has, therefore, high license com ...
,
Apache license,
Expat license
The MIT License is a permissive free software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts only very limited restriction on reuse and has, therefore, high license com ...
, and the various
BSD licenses
BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lice ...
.
Debate and controversy
It has been suggested that copyleft has become a divisive issue in the ideological strife between the
Open Source Initiative
The Open Source Initiative (OSI) is the steward of the Open Source Definition, the set of rules that define open source software. It is a California public-benefit nonprofit corporation,_with_501(c)(3).html" ;"title="110. - 6910./ref> is a type o ...
and the
free software movement
The free software movement is a social movement with the goal of obtaining and guaranteeing certain freedoms for software users, namely the freedoms to run the software, to study the software, to modify the software, and to share copies of the s ...
. However, there is evidence that copyleft is both accepted and proposed by both parties:
* Both the OSI and the FSF have copyleft and non-copyleft licenses in their respective lists of accepted licenses.
* The OSI's original Legal Counsel
Lawrence Rosen has written a copyleft license, the
Open Software License
The Open Software License (OSL) is a software license created by Lawrence Rosen. The Open Source Initiative (OSI) has certified it as an open-source license, but the Debian project judged version 1.1 to be incompatible with the DFSG. The OSL is ...
.
* The OSI's licensing how-to recognises the GPL as a "best practice" license.
* Some of the software programs of the GNU Project are published under non-copyleft licenses.
* Stallman himself has endorsed the use of non-copyleft licenses in certain circumstances, most recently in the case of the
Ogg Vorbis
Vorbis is a free and open-source software project headed by the Xiph.Org Foundation. The project produces an audio coding format and software reference encoder/decoder (codec) for lossy audio compression. Vorbis is most commonly used in conjun ...
license change.
Viral licensing
''Viral license'' is a pejorative name for copyleft licenses. It originates from the terms 'General Public Virus' or 'GNU Public Virus' (GPV), which dates back to 1990, a year after the GPLv1 was released. The name "
viral license
Viral license is an alternative name for copyleft licenses, especially the GPL, that allows derivative works only when permissions are preserved in modified versions of the work. Copyleft licenses include several common open-source and free co ...
s" refers to the fact that any works derived from a copyleft work must preserve the copyleft permissions when distributed.
Some advocates of the various
BSD Licenses
BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lice ...
used the term derisively in regards to the GPL's tendency to absorb BSD-licensed code without allowing the original BSD work to benefit from it, while at the same time promoting itself as "freer" than other licenses.
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...
vice-president
Craig Mundie
Craig James Mundie (born July 1, 1949 in Cleveland, Ohio) is Senior Advisor to the CEO at Microsoft and its former Chief Research and Strategy Officer.
Biography
He started in the consumer platforms division in 1992, managing the production of W ...
remarked, "This viral aspect of the GPL poses a threat to the intellectual property of any organization making use of it." In another context,
Steve Ballmer
Steven Anthony Ballmer (; March 24, 1956) is an American business magnate and investor who served as the chief executive officer of Microsoft from 2000 to 2014. He is the current owner of the Los Angeles Clippers of the National Basketball Associ ...
declared that code released under GPL is useless to the commercial sector, since it can only be used if the resulting surrounding code is licensed under a GPL-compatible license, and described it thus 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. According to
FSF compliance engineer David Turner, the term "viral license" creates a misunderstanding and a fear of using copylefted free software. While a person can catch a virus without active action, license conditions take effect upon effective usage or adoption. David McGowan has also written that there is no reason to believe the GPL could force proprietary software to become free software, but could "try to enjoin the firm from distributing commercially a program that combined with the GPL'd code to form a derivative work, and to recover damages for infringement." If the firm "actually copied code from a GPL'd program, such a suit would be a perfectly ordinary assertion of copyright, which most private firms would defend if the shoe were on the other foot." Richard Stallman has described this view with an analogy, saying, "The GPL's domain does not spread by proximity or contact, only by deliberate inclusion of GPL-covered code in your program. It spreads like a
spider plant, not like a virus."
Popular copyleft licenses, such as the GPL, have a clause allowing components to interact with non-copyleft components as long as the communication is abstract, such as executing a command-line tool with a set of switches or interacting with a web server. As a consequence, even if one module of an otherwise non-copyleft product is placed under the GPL, it may still be legal for other components to communicate with it in ways such as these. This allowed communication may or may not include reusing libraries or routines via
dynamic linking
In computing, a dynamic linker is the part of an operating system that loads and links the shared libraries needed by an executable when it is executed (at "run time"), by copying the content of libraries from persistent storage to RAM, filling ...
– some commentators say it does, the FSF asserts it does not and explicitly adds an
exception allowing it in the license for the
GNU Classpath
GNU Classpath is a free software implementation of the standard class library for the Java programming language. Most classes from J2SE 1.4 and 5.0 are implemented. Classpath can thus be used to run Java-based applications. GNU Classpath is a pa ...
re-implementation of the Java library. This ambiguity is an important difference between the GPL and 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 ...
, in that the LGPL specifically allows linking or compiling works licensed under terms that are not compatible with the LGPL, with works covered by the LGPL.
[Stallman, Richard]
Why you shouldn't use the Lesser GPL for your next library
GNU Project
The GNU Project () is a free software, mass collaboration project announced by Richard Stallman on September 27, 1983. Its goal is to give computer users freedom and control in their use of their computers and computing devices by collaborati ...
Symbol
The copyleft symbol is a mirror image of the
copyright symbol
The copyright symbol, or copyright sign, (a circled capital letter C for copyright), is the symbol used in copyright notices for works other than sound recordings. 17 U.S.C. The use of the symbol is described by the Universal Copyright Conv ...
, : a reversed in a circle. It has no legal status. A 2016 proposal to add the symbol to a future version of Unicode was accepted by the
Unicode Technical Committee
The Unicode Consortium (legally Unicode, Inc.) is a 501(c)(3) non-profit organization incorporated and based in Mountain View, California. Its primary purpose is to maintain and publish the Unicode Standard which was developed with the intentio ...
.
The code point was added in
Unicode 11.
[
it is largely unimplemented in fonts, but can be approximated with character or the more widely available character between parenthesis or, if supported by the application or web browser, by combining a reversed c with the character : .]
''For a list of fonts that include this glyph, see and then row "Enclosed Alphanumeric Supplement
Enclosed Alphanumeric Supplement is a Unicode block consisting of Latin alphabet characters and Arabic numerals enclosed in circles, ovals or boxes, used for a variety of purposes. It is encoded in the range U+1F100–U+1F1FF in the Supplem ...
(173: 1F100–1F1FF)" (This list is not guaranteed to be current).''
See also
*
* All rights reversed
All rights reversed is a phrase that indicates a release of copyright or a copyleft licensing status. It is a pun on the common copyright disclaimer "All rights reserved", a copyright formality originally required by the Buenos Aires Conventio ...
* Anti-copyright notice
An anti-copyright notice is a specific statement that is added to a work in order to encourage wide distribution. Such notices are legally required to host such specific media; under the Berne Convention in international copyright law, works are p ...
* Commercial use of copyleft works
The commercialization of copylefted works differs from proprietary works. The economic focus tends to be on the commercialization of other scarcities, and complimentary goods rather than the free works themselves. One way to make money with copylef ...
* Comparison of open source and closed source
Free/open-source software – the source availability model used by free and open-source software (FOSS) – and closed source are two approaches to the distribution of software.
Background
Under the ''closed-source'' model source code is ...
* Copyfraud
A copyfraud is a false copyright claim by an individual or institution with respect to content that is in the public domain. Such claims are wrongful, at least under US and Australian copyright law, because material that is not copyrighted is f ...
* Copyright
A copyright is a type of intellectual property that gives its owner the exclusive right to copy, distribute, adapt, display, and perform a creative work, usually for a limited time. The creative work may be in a literary, artistic, education ...
* Copyright alternatives Various copyright alternatives in an alternative compensation systems (ACS) have been proposed as ways to allow the widespread reproduction of digital copyrighted works while still paying the authors and copyright owners of those works. This article ...
* Creative Commons licenses
A Creative Commons (CC) license is one of several public copyright licenses that enable the free distribution of an otherwise copyrighted "work".A "work" is any creative material made by a person. A painting, a graphic, a book, a song/lyrics ...
* Criticism of intellectual property
Intellectual property (IP) is a category of property that includes intangible creations of the human intellect. There are many types of intellectual property, and some countries recognize more than others. The best-known types are patents, cop ...
* Internet freedom Internet freedom is an umbrella term that encompasses digital rights, freedom of information, the right to Internet access, freedom from Internet censorship, and net neutrality.
Some believe that Internet freedom is not a human right. They think t ...
* Free Art License
The Free Art License (FAL), (french: Licence Art Libre (LAL)) is a copyleft license that grants the right to freely copy, distribute, and transform creative works.
History
The license was written in July 2000 with contributions from the mailin ...
* Free content
* Free Culture movement
The free-culture movement is a social movement that promotes the freedom to distribute and modify the creative works of others in the form of free content or open content without compensation to, or the consent of, the work's original creators, ...
* Free software movement
The free software movement is a social movement with the goal of obtaining and guaranteeing certain freedoms for software users, namely the freedoms to run the software, to study the software, to modify the software, and to share copies of the s ...
* GNU General Public License
The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the Four Freedoms (Free software), four freedoms to run, study, share, and modify the software. The license was th ...
* HESSLA – a license that prohibits uses that violate human rights or add spyware
* History of free and open-source software
In the 1950s and 1960s, computer operating software and compilers were delivered as a part of hardware purchases without separate fees. At the time, source code, the human-readable form of software, was generally distributed with the software p ...
* Kopimi
* Open content
* 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. The open-source model is a decentralized sof ...
* Opposition to copyright
Criticism of copyright, or anti-copyright sentiment, is a dissenting view of the current state of copyright law or copyright as a concept. Critics often discuss philosophical, economical, or social rationales of such laws and the laws' implem ...
* Patentleft
Patentleft is the practice of licensing patents (especially biological patents) for royalty-free use, on the condition that adopters license related improvements they develop under the same terms. Copyleft-style licensors seek "continuous grow ...
* Permissive free-software licence
* Public copyright license
A public license or public copyright licenses is a license by which a copyright holder as licensor can grant additional copyright permissions to any and all persons in the general public as licensees.
By applying a public license to a work, pro ...
* Public domain
The public domain (PD) consists of all the creative work
A creative work is a manifestation of creative effort including fine artwork (sculpture, paintings, drawing, sketching, performance art), dance, writing (literature), filmmaking, ...
* Share-alike
Share-alike (🄎) is a copyright licensing term, originally used by the Creative Commons project, to describe works or licenses that require copies or adaptations of the work to be released under the same or similar license as the original. Copy ...
* ''Steal This Film
''Steal This Film'' is a film series documenting the movement against intellectual property directed by Jamie King, produced by The League of Noble Peers and released via the BitTorrent peer-to-peer protocol.
Two parts, and one special The ...
''
References
{{Intellectual property activism
Copyright law
Free software
Intellectual property activism
Free and open-source software licenses
Typographical symbols