![Software licensing spectrum](https://upload.wikimedia.org/wikipedia/commons/f/f0/Software_licensing_spectrum.png)
A free-software license is a notice that grants the recipient of a piece of software extensive rights to modify and
redistribute that software. These actions are usually prohibited by
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, educatio ...
law, but the rights-holder (usually the author) of a piece of software can remove these restrictions by accompanying the software with a
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 ...
which grants the recipient these rights. Software using such a license is free software (or
free and open-source software) as conferred by the copyright holder. Free-software licenses are applied to
software
Software is a set of computer programs and associated software documentation, documentation and data (computing), data. This is in contrast to Computer hardware, hardware, from which the system is built and which actually performs the work.
...
in
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 w ...
and also binary
object-code form, as the copyright law recognizes both forms.
Comparison
Free-software licenses provide risk mitigation against different legal threats or behaviors that are seen as potentially harmful by developers:
History
Pre-1980s
In the early times of software, sharing of software and source code was common in certain communities, for instance academic institutions.
Before the US Commission on New Technological Uses of Copyrighted Works (CONTU) decided in 1974 that "computer programs, to the extent that they embody an author's original creation, are proper subject matter of copyright",
[Lemley, Menell, Merges and Samuelson. ''Software and Internet Law'', p. 34.] software was not considered copyrightable. Therefore, software had no licenses attached and was shared as
public-domain software
Public-domain software is software that has been placed in the public domain, in other words, software for which there is absolutely no ownership such as copyright, trademark, or patent. Software in the public domain can be modified, distributed, ...
. The CONTU decision plus court decisions such as ''
Apple v. Franklin'' in 1983 for
object code
In computing, object code or object module is the product of a compiler
In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ...
, clarified that the Copyright Act gave computer programs the copyright status of literary works and started the
licensing of software.
Free-software licenses before the late 1980s were generally informal notices written by the developers themselves. These early licenses were of the "
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 ...
" kind.
1980s
In the mid-1980s, 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 collaborat ...
produced
copyleft
Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose ...
free-software licenses for each of its software packages. An early such license (the "GNU Emacs Copying Permission Notice") was used for
GNU Emacs
GNU Emacs is a free software text editor. It was created by GNU Project founder Richard Stallman, based on the Emacs editor developed for Unix operating systems. GNU Emacs has been a central component of the GNU project and a flagship project of ...
in 1985, which was revised into the "GNU Emacs General Public License" in late 1985, and clarified in March 1987 and February 1988. Likewise, the similar GCC General Public License was applied to the
GNU Compiler Collection
The GNU Compiler Collection (GCC) is an optimizing compiler produced by the GNU Project supporting various programming languages, hardware architectures and operating systems. The Free Software Foundation (FSF) distributes GCC as free softwar ...
, which was initially published in 1987. The
original BSD license
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 ...
is also one of the first free-software licenses, dating to 1988. In 1989, version1 of 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 to run, study, share, and modify the software. The license was the first copyleft for general ...
(GPL) was published. Version2 of the GPL, released in 1991, went on to become the most widely used free-software license.
1990s to 2000s
Starting in the mid-1990s and until the mid-2000s, the
open-source movement pushed and focused the free-software idea forward in the wider public and business perception. In the
Dot-com bubble
The dot-com bubble (dot-com boom, tech bubble, or the Internet bubble) was a stock market bubble in the late 1990s, a period of massive growth in the use and adoption of the Internet.
Between 1995 and its peak in March 2000, the Nasdaq Compo ...
time,
Netscape Communications
Netscape Communications Corporation (originally Mosaic Communications Corporation) was an American independent computer services company with headquarters in Mountain View, California and then Dulles, Virginia. Its Netscape web browser was onc ...
' step to release its webbrowser under a FOSS license in 1998,
inspired many other companies to adapt to the FOSS ecosystem. In this trend companies and new projects (
Mozilla
Mozilla (stylized as moz://a) is a free software community founded in 1998 by members of Netscape. The Mozilla community uses, develops, spreads and supports Mozilla products, thereby promoting exclusively free software and open standards, w ...
,
Apache foundation
The Apache Software Foundation (ASF) is an American nonprofit corporation (classified as a 501(c)(3) organization in the United States) to support a number of open source software projects. The ASF was formed from a group of developers of the ...
, and
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
, see also
this list) wrote their own FOSS licenses, or adapted existing licenses. This
License proliferation
License proliferation is the phenomenon of an abundance of already existing and the continued creation of new software licenses for software and software packages in the FOSS ecosystem. License proliferation affects the whole FOSS ecosystem neg ...
was later recognized as problem for the
Free and open-source ecosystem due to the increased complexity of
license compatibility
License compatibility is a legal framework that allows for pieces of software with different software licenses to be distributed together. The need for such a framework arises because the different licenses can contain contradictory requirement ...
considerations. While the creation of new licenses slowed down later, license proliferation and its impact are considered an ongoing serious challenge for the free and open-source ecosystem.
From the free-software licenses, the GNU GPL version2 has been tested in to court, first in Germany in 2004 and later in the USA. In the German case the judge did not explicitly discuss the validity of the GPL's clauses but accepted that the GPL had to be adhered to: "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." Because the defendant did not comply with the GPL, it had to cease use of the software. The US case (
MySQL
MySQL () is an open-source relational database management system (RDBMS). Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, and "SQL", the acronym for Structured Query Language. A relational database ...
vs Progress) was settled before a verdict was arrived at, but at an initial hearing, Judge Saris "saw no reason" that the GPL would not be enforceable.
Around 2004 lawyer
Lawrence Rosen argued in the essay ''Why the public domain isn't a license'' software could not truly be waived into public domain and can't be interpreted as very permissive FOSS license, a position which faced opposition by
Daniel J. Bernstein and others. In 2012 the dispute was finally resolved when Rosen accepted the
CC0
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/lyric ...
as
open source license
An open-source license is a type of license for computer software and other products that allows the source code, blueprint or design to be used, modified and/or shared under defined terms and conditions. This allows end users and commercial compa ...
, while admitting that contrary to his previous claims copyright can be waived away, backed by
Ninth circuit
The United States Court of Appeals for the Ninth Circuit (in case citations, 9th Cir.) is the U.S. federal court of appeals that has appellate jurisdiction over the U.S. district courts in the following federal judicial districts:
* District ...
decisions.
In 2007, after years of draft discussion, the GPLv3 as major update of the GPLv2 was released. The release was controversial due to the significant extended scope of the license, which made it incompatible with the GPLv2.
Several major FOSS projects (
Linux kernel,
MySQL
MySQL () is an open-source relational database management system (RDBMS). Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, and "SQL", the acronym for Structured Query Language. A relational database ...
,
BusyBox
BusyBox is a software suite that provides several Unix utilities in a single executable file. It runs in a variety of POSIX environments such as Linux, Android, and FreeBSD, although many of the tools it provides are designed to work with in ...
,
Blender
A blender (sometimes called a mixer or liquidiser in British English) is a kitchen and laboratory appliance used to mix, crush, purée or emulsify food and other substances. A stationary blender consists of a blender container with a rotating me ...
,
VLC media player
VLC media player (previously the VideoLAN Client and commonly known as simply VLC) is a free and open-source, portable, cross-platform media player software and streaming media server developed by the VideoLAN project. VLC is available for desk ...
) decided against adopting the GPLv3.
On the other hand, in 2009, two years after the release of the GPLv3,
Google
Google LLC () is an American Multinational corporation, multinational technology company focusing on Search Engine, search engine technology, online advertising, cloud computing, software, computer software, quantum computing, e-commerce, ar ...
open-source programs office manager Chris DiBona reported that the number of open-source projects licensed software that had moved to GPLv3 from GPLv2 was 50%, counting the projects hosted at
Google Code
Google Developers (previously Google Code) , application programming interfaces (APIs), and technical resources. The site contains documentation on using Google developer tools and APIs—including discussion groups and blogs for developers usi ...
.
2010s
In 2011, four years after the release of the GPLv3, 6.5% of all open-source licensed projects were GPLv3 while 42.5% were still 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.
In 2015 according to Black Duck Software
and
GitHub
GitHub, Inc. () is an Internet hosting service for software development and version control using Git. It provides the distributed version control of Git plus access control, bug tracking, software feature requests, task management, continu ...
statistics,
the permissive
MIT 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 comp ...
dethroned the GPLv2 as most popular free-software license to the second place while the permissive
Apache license follows already at third place. In June 2016 an analysis of
Fedora Project
The Fedora Project is an independent project to co-ordinate the development of Fedora Linux, a Linux-based operating system, operating with the vision of "''a world where everyone benefits from free and open source software built by inclusive, w ...
's packages revealed as most used licenses the GPL, MIT, BSD, and the
LGPL.
Definitions
OSI-approved open-source licenses
The group
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 ...
(OSI) defines and maintains a list of approved
open-source license
An open-source license is a type of license for computer software and other products that allows the source code, blueprint or design to be used, modified and/or shared under defined terms and conditions. This allows end users and commercial compa ...
s. OSI agrees with FSF on all widely used free-software licenses, but differ from FSF's list, as it approves against 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 ...
rather than 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 ...
. It considers Free Software Permissive license group to be a reference implementation of a Free Software license. Thus its requirements for approving licenses are different.
FSF-approved free-software licenses
The
Free Software Foundation
The Free Software Foundation (FSF) is a 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 under copyleft (" ...
, the group that maintains 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 ...
, maintains a non-exhaustive list of free-software licences.
The Free Software Foundation prefers
copyleft
Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose ...
(
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. Cop ...
) free-software licensing rather than permissive free-software licensing for most purposes. Its list distinguishes between free-software licenses that are compatible or incompatible with the FSF's copyleft
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 to run, study, share, and modify the software. The license was the first copyleft for general ...
.
Conditions in free-software licenses
There exists an ongoing debate within the
free-software community regarding the fine line between what restrictions can be applied and still be called "free".
Only "
public-domain software
Public-domain software is software that has been placed in the public domain, in other words, software for which there is absolutely no ownership such as copyright, trademark, or patent. Software in the public domain can be modified, distributed, ...
" and software under a
public-domain-like license is restriction-free. Examples of public-domain-like licenses are, for instance, the
WTFPL
WTFPL is a permissive free software license. As a public domain like license, the WTFPL is essentially the same as dedication to the public domain. It allows redistribution and modification of the work under any terms. The title is an abbreviat ...
and the
CC0
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/lyric ...
license.
Permissive license
A permissive software license, sometimes also called BSD-like or BSD-style license, is a free-software license which instead of copyleft protections, carries only minimal restrictions on how the software can be used, modified, and redistributed, ...
s might carry small obligations like
attribution of the author but allow practically all code use cases. Certain licenses, namely the
copyleft licenses, include intentionally stronger restrictions (especially on the distribution/distributor) in order to force derived projects to guarantee specific rights which can't be taken away.
Copyleft
The free-software share-alike licenses 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 ...
in the mid-1980s pioneered a concept known as "copyleft". Ensuing copyleft provisions stated that when modified versions of free software are distributed, they must be distributed under the same terms as the original software. Hence they are referred to as "share and
share alike" or "''quid pro quo''". This results in the new software being open source as well. Since copyleft ensures that later generations of the software grant the freedom to modify the code, this is "free software". Non-copyleft licenses do not ensure that later generations of the software will remain free.
Developers who use GPL code in their product must make 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 w ...
available to anyone when they share or sell the
object code
In computing, object code or object module is the product of a compiler
In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ...
. In this case, the source code must also contain any changes the developers may have made. If GPL code is used but not shared or sold, the code is not required to be made available and any changes may remain private. This permits developers and organizations to use and modify GPL code for private purposes (that is, when the code or the project is not sold or otherwise shared) without being required to make their changes available to the public.
Supporters of GPL claim that by mandating that derivative works remain under the GPL, it fosters the growth of free software and requires equal participation by all users. Opponents of GPL claim that "no license can guarantee future software availability" and that the disadvantages of GPL outweigh its advantages. Some also argue that restricting distribution makes the license less free. Whereas proponents would argue that not preserving freedom during distribution would make it less free. For example, a non-copyleft license does not grant the author the freedom to see modified versions of his or her work if it gets publicly published, whereas a copyleft license does grant that freedom.
Patent retaliation
During the 1990s, free-software licenses began including clauses, such as
patent retaliation
Opposition to software patents is widespread in the free software community. In response, various mechanisms have been tried to defuse the perceived problem.
Positions from the community
Community leaders such as Richard Stallman, Alan Cox, B ...
, in order to protect against
software patent
A software patent is a patent on a piece of software, such as a computer program, libraries, user interface, or algorithm.
Background
A patent is a set of exclusionary rights granted by a state to a patent holder for a limited period of time, u ...
litigation cases – a problem which had not previously existed. This new threat was one of the reasons for writing version3 of the GNU GPL in 2006. In recent years, a term coined
tivoization
Tivoization is the practice of designing hardware that incorporates software under the terms of a copyleft software license like the GNU General Public License (GNU GPL), but uses hardware restrictions or digital rights management (DRM) to preve ...
describes a process where hardware restrictions are used to prevent users from running modified versions of the software on that hardware, in which the
TiVo
TiVo ( ) is a digital video recorder (DVR) developed and marketed by Xperi (previously by TiVo Corporation and TiVo Inc.) and introduced in 1999. TiVo provides an on-screen guide of scheduled broadcast programming television programs, whose fea ...
device is an example. It is viewed by the FSF as a way to turn free software to effectively non-free, and is why they have chosen to prohibit it in
GPLv3
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 to run, study, share, and modify the software. The license was the first copyleft for general u ...
.
Most newly written free-software licenses since the late 1990s include some form of patent retaliation clauses. These measures stipulate that one's rights under the license (such as to redistribution), may be terminated if one attempts to enforce patents relating to the licensed software, under certain circumstances. As an example, the
Apple Public Source License
The Apple Public Source License (APSL) is the open-source and free software license under which Apple's Darwin operating system was released in 2000. A free and open-source software license was voluntarily adopted to further involve the communit ...
may terminate a user's rights if said user embarks on litigation proceedings against them due to patent litigation. Patent retaliation emerged in response to proliferation and abuse of
software patents
A software patent is a patent on a piece of software, such as a computer program, libraries, user interface, or algorithm.
Background
A patent is a set of exclusionary rights granted by a state to a patent holder for a limited period of time, u ...
.
Hardware restrictions
Version3 of the GNU GPL includes specific language prohibiting additional restrictions being enforced by
hardware restrictions
A hardware restriction (sometimes called hardware DRM) is low-level protection enforced by electronic components. The hardware restriction scheme may protect against physical or malware attacks or complement a digital rights management system imp ...
and
digital rights management (DRM), a practice FSF calls
tivoization
Tivoization is the practice of designing hardware that incorporates software under the terms of a copyleft software license like the GNU General Public License (GNU GPL), but uses hardware restrictions or digital rights management (DRM) to preve ...
after
Tivo
TiVo ( ) is a digital video recorder (DVR) developed and marketed by Xperi (previously by TiVo Corporation and TiVo Inc.) and introduced in 1999. TiVo provides an on-screen guide of scheduled broadcast programming television programs, whose fea ...
used GPL’d software on devices that disallowed user modification of that software.
Attribution, disclaimers and notices
The majority of free-software licenses require that modified software not claim to be unmodified. Some licenses also require that copyright holders be credited. One such example is version2 of the GNU GPL, which requires that interactive programs that print warranty or license information, may not have these notices removed from modified versions intended for distribution.
Practical problems with licenses
License compatibility
![Floss-license-slide-image](https://upload.wikimedia.org/wikipedia/commons/2/2b/Floss-license-slide-image.svg)
Licenses of software packages containing contradictory requirements render it impossible to combine source code from such packages in order to create new software packages. License compatibility between a
copyleft license and another license is often only a one-way compatibility. This "one-way compatibility" characteristic is, for instanced, criticized by the
Apache Foundation
The Apache Software Foundation (ASF) is an American nonprofit corporation (classified as a 501(c)(3) organization in the United States) to support a number of open source software projects. The ASF was formed from a group of developers of the ...
, who provides the more
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 ...
Apache license which doesn't have this characteristic. Non-copyleft licenses, such as the FOSS
permissive licenses, have a less complicated license interaction and normally exhibit better license compatibility.
For example, if one license says "modified versions must mention the developers in any advertising materials", and another license says "modified versions cannot contain additional attribution requirements", then, if someone combined a software package which uses one license with a software package which uses the other, it would be impossible to distribute the combination because these contradictory requirements cannot be fulfilled simultaneously. Thus, these two packages would be license-incompatible. When it comes to
copyleft
Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose ...
software licenses, they are not inherently compatible with other copyleft licenses, even the GPLv2 is, by itself, not compatible with the GPLv3.
Purpose of use
Restrictions on use of a software ("use restrictions") are generally unacceptable according to the FSF,
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 ...
,
Debian, or the BSD-based distributions. Examples include prohibiting that the software be used for non-private applications, for military purposes, for comparison or benchmarking, for good use, for ethically questionable means, or in commercial organizations.
While some restrictions on user freedom, e.g. concerning nuclear war, seem to enjoy moral support among most free software developers, it is generally believed that such agendas should not be served through software licenses; among other things because of practical aspects such as resulting legal uncertainties and problems with enforceability of vague, broad and/or subjective criteria or because tool makers are generally not held responsible for other people’s use of their tools. Nevertheless some projects include legally non-binding pleas to the user, prominently
SQLite
SQLite (, ) is a database engine written in the C programming language. It is not a standalone app; rather, it is a library that software developers embed in their apps. As such, it belongs to the family of embedded databases. It is the m ...
. Among the repeated attempts by developers to regulate user behavior through the license that sparked wider debate are
Douglas Crockford
Douglas Crockford is an American computer programmer who is involved in the development of the JavaScript language. He specified the data format JSON (JavaScript Object Notation), and has developed various JavaScript related tools such as the st ...
’s (joking) “no evil” clause, which affected the release process of the Debian distribution in 2012 and got the JSMin-PHP project expelled from
Google Code
Google Developers (previously Google Code) , application programming interfaces (APIs), and technical resources. The site contains documentation on using Google developer tools and APIs—including discussion groups and blogs for developers usi ...
, the addition of a pacifist condition based on
Asimov’s First Law of Robotics to the GPL for the distributed computing software ''GPU'' in 2005, as well as several software projects trying to exclude use by big cloud providers.
Definition conflicts
As there are several defining organizations and groups who publish definitions and guidelines about FOSS licenses, notably the FSF, the OSI, the Debian project, and the BSDs, there are sometimes conflicting opinions and interpretations.
Permissive versus copyleft opinions
Many users and developers of
BSD
The Berkeley Software Distribution or Berkeley Standard Distribution (BSD) is a discontinued operating system based on Research Unix, developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berk ...
-based operating systems have a different position on licensing. The main difference is the belief that the
copyleft
Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose ...
licenses, particularly 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 to run, study, share, and modify the software. The license was the first copyleft for general ...
(GPL), are undesirably complicated and/or restrictive. The GPL requires any derivative work to also be released according to the GPL while the
BSD license
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 ...
does not. Essentially, the BSD license's only requirement is to acknowledge the original authors, and poses no restrictions on how 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 w ...
may be used.
As a result, BSD code can be used in
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 i ...
that only acknowledges the authors. For instance,
Microsoft Windows NT 3.1
Windows NT 3.1 is the first major release of the Windows NT operating system developed by Microsoft, released on July 27, 1993.
At the time of Windows NT's release, Microsoft's Windows 3.1 desktop environment had established brand recognition ...
and
macOS
macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...
have proprietary
IP stacks which are derived from BSD-licensed software. In extreme cases, the sub- or re-licensing possibilities with BSD or other permissive licenses might prevent further use in the open-source ecosystem. For instance,
MathWorks
MathWorks is an American privately held corporation that specializes in mathematical computing software. Its major products include MATLAB and Simulink, which support data analysis and simulation.
History
The company's key product, MATLAB, was ...
' FileExchange repository offers the BSD license for user contributions but prevents with additional
terms of use any usage beside their own