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A permissive software license, sometimes also called BSD-like or BSD-style license, is a free-software
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 ...
which instead of
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 ...
protections, carries only minimal restrictions on how the software can be used, modified, and redistributed, usually including a warranty disclaimer. Examples include the
GNU All-permissive License The GNU All-permissive License is a lax, permissive (non-copyleft) free software license, compatible with the GNU General Public License, recommended by the Free Software Foundation for README and other small supporting files (under 300 line ...
, MIT License,
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 li ...
,
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 communi ...
and Apache license. the most popular free-software license is the permissive MIT license.


Example

The following is the full text of the simple
GNU All-permissive License The GNU All-permissive License is a lax, permissive (non-copyleft) free software license, compatible with the GNU General Public License, recommended by the Free Software Foundation for README and other small supporting files (under 300 line ...
:


Definitions

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) tax-exempt status. The organization wa ...
defines a permissive software license as a "non-
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 ...
license that guarantees the freedoms to use, modify and redistribute".
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, cont ...
's ''choosealicense'' website describes the permissive MIT license as " ettingpeople do anything they want with your code as long as they provide attribution back to you and don’t hold you
liable In law, liable means "responsible or answerable in law; legally obligated". Legal liability concerns both civil law and criminal law and can arise from various areas of law, such as contracts, torts, taxes, or fines given by government agen ...
." California Western School of Law's newmediarights.com defined them as follows: "The ‘BSD-like’ licenses such as the BSD, MIT and Apache licenses are extremely permissive, requiring little more than attributing the original portions of the licensed code to the original developers in your own code and/or documentation."


Comparison to copyleft

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 generally require the reciprocal publication of the source code of any modified versions under the original work's copyleft license. Permissive licenses, in contrast, do not try to guarantee that modified versions of the software will remain free and publicly available, generally requiring only that the original copyright notice be retained. As a result, derivative works, or future versions, of permissively-licensed software can be released as proprietary software. Defining how liberal a license is, however, is not something easily quantifiable, and often depends on the goals of the final users. If the latter are developers, for some it might be valuable to have the right to modify and exploit source code written by others and possibly incorporate it into proprietary code and make money with it (and therefore these see permissive licenses as offering them a "right"), while for other developers it might be more valuable to know that nobody will ever capitalize what has mostly been their work (and therefore these see copyleft licenses as offering them a "right"). Furthermore, the final users might not be developers at all, and in this case copyleft licenses offer them the everlasting right to access a software as free software, ensuring that it will never become closed source – while permissive licenses offer no rights at all to non-developer final users, and software released with a permissive license could theoretically become from one day to another a closed source malware without the user even knowing it. Permissive licenses offer more extensive
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 requiremen ...
than copyleft licenses, which cannot generally be freely combined and mixed, because their reciprocity requirements conflict with each other.


Comparison to public domain

Computer Associates Int'l v. Altai used the term "public domain" to refer to works that have become widely shared and distributed under permission, rather than work that was deliberately put into the public domain. However, permissive licenses are not actually equivalent to releasing a work into the
public domain The public domain (PD) consists of all the creative work to which no exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly waived, or may be inapplicable. Because those rights have expired ...
. Permissive licenses often do stipulate some limited requirements, such as that the original authors must be credited (''attribution''). If a work is truly in the public domain, this is usually not legally required, but a United States copyright registration requires disclosing material that has been previously published, and attribution may still be considered an ethical requirement in
academia An academy (Attic Greek: Ἀκαδήμεια; Koine Greek Ἀκαδημία) is an institution of secondary education, secondary or tertiary education, tertiary higher education, higher learning (and generally also research or honorary membershi ...
. Advocates of permissive licenses often recommend against attempting to release software to the public domain, on the grounds that this can be legally problematic in some jurisdictions. Public-domain-equivalent licenses are an attempt to solve this problem, providing a fallback permissive license for cases where renunciation of copyright is not legally possible, and sometimes also including a disclaimer of warranties similar to most permissive licenses.


License compatibility

In general permissive licenses have good
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 requiremen ...
with most other software licenses in most situations. Due to their non-restrictiveness, most permissive software licenses are even compatible with copyleft licenses, which are incompatible with most other licenses. Some older permissive licenses, such as the 4-clause BSD license, the PHP License, and the
OpenSSL License OpenSSL is a software library for applications that provide secure communications over computer networks against eavesdropping or need to identify the party at the other end. It is widely used by Internet servers, including the majority of ...
, have clauses requiring advertising materials to credit the copyright holder, which made them incompatible with copyleft licenses. Popular modern permissive licenses, however, such as the MIT License, the 3-clause BSD license and the zlib license, don't include advertising clauses and are generally compatible with copyleft licenses. Some licenses do not allow derived works to add a restriction that says a redistributor cannot add more restrictions. Examples include the
CDDL The Common Development and Distribution License (CDDL) is a free and open-source software license, produced by Sun Microsystems, based on the Mozilla Public License (MPL). Files licensed under the CDDL can be combined with files licensed under ...
and
MsPL MSPL Limited is an Indian company that operates iron ore mines and wind farms. It is a subsidiary of the Baldota Group. Iron Mining MSPL mines, processes and exports iron ore. According to the Federation of Indian Mineral Industries, It ...
. However such restrictions also make the license incompatible with permissive free-software licenses.


Reception and adoption

While they have been in use since the mid-1980s, several authors noted an increase in the popularity of permissive licenses during the 2010s. the MIT License, a permissive license, is the most popular free software license, followed by GPLv2.


Other terms


Non-copyleft

Sometimes the word "permissive" is considered too ambiguous, because all free software licenses are "permissive", in the sense that they all allow to modify and redistribute the source code. In most cases the real opposition is between
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 and non-copyleft ones, thus some authors prefer to use the term "non-copyleft" instead of "permissive".


Copycenter

''Copycenter'' is a term originally used to explain the modified BSD license, a permissive free-software license. The term was presented by
computer scientist A computer scientist is a person who is trained in the academic study of computer science. Computer scientists typically work on the theoretical side of computation, as opposed to the hardware side on which computer engineers mainly focus (a ...
and
Berkeley Software Distribution 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, Be ...
(BSD) contributor
Marshall Kirk McKusick Marshall Kirk McKusick (born January 19, 1954) is a computer scientist, known for his extensive work on BSD UNIX, from the 1980s to FreeBSD in the present day. He was president of the USENIX Association from 1990 to 1992 and again from 2002 to ...
at a BSD conference in 1999. It is a
word play Word play or wordplay (also: play-on-words) is a literary technique and a form of wit in which words used become the main subject of the work, primarily for the purpose of intended effect or amusement. Examples of word play include puns, pho ...
on
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 ...
,
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 ...
and copy center.


Pushover license

In 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 ( ...
's guide to license compatibility and relicensing,
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 ...
defines permissive licenses as "pushover licenses", comparing them to those people who "can't say no", because they are seen as granting a right to "deny freedom to others." The Foundation recommends pushover licenses only for small programs, below 300 lines of code, where "the benefits provided by copyleft are usually too small to justify the inconvenience of making sure a copy of the license always accompanies the software".


Cuck license

In response to those corporations that put pressure on developers to move away from
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 in favour of permissive ones, some developers have coined the term "cuck license" (precisely in analogy to being
cuckolded A cuckold is the husband of an adulterous wife; the wife of an adulterous husband is a cuckquean. In biology, a cuckold is a male who unwittingly invests parental investment, parental effort in juveniles who are not genetically his offspring. ...
), as they perceive that corporations want to benefit from collaborative work and privatize profits without giving anything back.


See also

* *
License-free software License-free software is computer software that is not explicitly in the public domain, but the authors appear to intend free use, modification, distribution and distribution of the modified software, similar to the freedoms defined for free soft ...
*
Public domain equivalent license Public-domain-equivalent license are licenses that grant public-domain-like rights and/or act as waivers. They are used to make copyrighted works usable by anyone without conditions, while avoiding the complexities of attribution or license com ...
*
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 software. These actions are usually prohibited by copyright law, but the rights-holder (usually the author ...
*
Comparison of free and open-source software licenses This comparison only covers software licenses which have a linked Wikipedia article for details and which are approved by at least one of the following expert groups: the Free Software Foundation, the Open Source Initiative, the Debian Project an ...
*
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 ( ...


References


External links

{{FOSS Free and open-source software licenses