Public-domain-equivalent license are

license A license (American English) or licence (Commonwealth English) 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 part ...

s that grant public-domain-like rights and/or act as

waiver A waiver is the voluntary relinquishment or surrender of some known right or privilege. A waiver is often written, such as a disclaimer that has been accepted, but it may also be spoken between two or more parties. When the right to hold a ...

s. They are used to make copyrighted works usable by anyone without conditions, while avoiding the complexities of attribution or license compatibility that occur with other licenses. No permission or license is required for a work truly in the public domain, such as one with an expired copyright; such a work may be copied at will. Public domain equivalent licenses exist because some legal jurisdictions do not provide for authors to voluntarily place their work in the public domain, but do allow them to grant arbitrarily broad rights in the work to the public. The licensing process also allows authors, particularly software authors, the opportunity to explicitly deny any implied warranty that might give someone a basis for legal action against them. While there is no universally agreed-upon license, several licenses aim to grant the same rights that would apply to a work in the public domain.

Licenses

WTFPL

In 2000, the "Do What the Fuck You Want To Public License" ( WTFPL) was released as a public-domain-equivalent license for software. It is distinguished among software licenses by its informal style and lack of a

warranty In law, a warranty is an expressed or implied promise or assurance of some kind. The term's meaning varies across legal subjects. In property law, it refers to a covenant by the grantor of a deed. In insurance law, it refers to a promise by the ...

disclaimer A disclaimer is generally any statement intended to specify or delimit the scope of rights and obligations that may be exercised and enforced by parties in a legally recognized relationship. In contrast to other terms for legally operative langua ...

. In 2016, according to Black Duck Software, the WTFPL was used by less than 1% of FOSS projects.

CC0

In 2009,

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 ...

released CC0, which was created for compatibility with jurisdictions where dedicating to public domain is problematic, such as

continental Europe Continental Europe or mainland Europe is the contiguous mainland of Europe, excluding its surrounding islands. It can also be referred to ambiguously as the European continent, – which can conversely mean the whole of Europe – and, by som ...

. This is achieved by a public-domain waiver statement and a fall-back all-

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, ...

, for cases where the waiver is not valid. 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. The organisation supports the free software movement, with the organization's preference for software being distributed ...

and the Open Knowledge Foundation approved CC0 as a recommended license to dedicate content to the public domain. The FSF and the Open Source Initiative, however, do not recommend the usage of this license for software due to inclusion of a clause expressly stating it does not grant patent licenses. In June 2016 an analysis of the Fedora Project's software packages placed CC0 as the 17th most popular license.

Unlicense

The Unlicense software license, published around 2010, offers a public-domain waiver text with a fall-back public-domain-like license, inspired by permissive licenses but without an attribution clause. In 2015 GitHub reported that approximately 102,000 of their 5.1 million licensed projects, or 2%, use the Unlicense.

0BSD

The BSD Zero Clause License, published in 2013, removes half a sentence from the ISC license, leaving only an unconditional grant of rights and a warranty disclaimer. It is listed by the Software Package Data Exchange as the Zero Clause BSD license, with the SPDX identifier 0BSD. It was first used by Rob Landley in Toybox and is OSI-approved.

MIT-0

The MIT No Attribution License, a variation of the MIT License, was published in 2018 and has the identifier MIT-0 in the SPDX License List.

Reception

In the free-software community, there has been some controversy over whether a

public domain The public domain (PD) consists of all the creative work to which no Exclusive exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly Waiver, waived, or may be inapplicable. Because no one holds ...

dedication constitutes a valid

open-source license Open-source licenses are software licenses that allow content to be used, modified, and shared. They facilitate free and open-source software (FOSS) development. Intellectual property (IP) laws restrict the modification and sharing of creative ...

. In 2004, lawyer Lawrence Rosen argued in the essay "Why the public domain isn't a license" that software could not truly be given into public domain, a position that faced opposition by Daniel J. Bernstein and others. In 2012, Rosen changed his mind, accepted CC0 as an open-source license, and admitted that, contrary to his previous claims, copyright can be waived away. In 2011, the

added CC0 to its free software licenses and called it "the preferred method of releasing software in the public domain" – the Foundation then reviewed its position specifically for softwares. In February 2012, when the CC0 license was submitted to the Open Source Initiative for approval, controversy arose over a clause which excluded any relevant patents held by the copyright holder from the scope of the license. This clause was added with scientific data in mind rather than software, but some members of the OSI believed it could weaken users' defenses against

software patent A software patent is a patent on a piece of software, such as a computer program, library, user interface, or algorithm. The validity of these patents can be difficult to evaluate, as software is often at once a product of engineering, something ...

s. As a result, Creative Commons withdrew their submission, and the license is not currently approved by the OSI. In July 2022, the Fedora Project deprecated CC0 for software code for the same reasons, but will still allow its use for non-code content. In June 2020, following a request for legacy approval, OSI formally recognized the Unlicense as an approved license meeting the OSD.

Google Google LLC (, ) is an American multinational corporation and technology company focusing on online advertising, search engine technology, cloud computing, computer software, quantum computing, e-commerce, consumer electronics, and artificial ...

does not allow its employees to contribute to projects under public domain equivalent licenses like the Unlicense and CC0, while allowing contributions to 0BSD licensed and US government PD projects.

Notes

References

{{Reflist , refs = {{cite web , url = http://anonscm.debian.org/viewvc/pkg-wmaker/trunk/COPYING.WTFPL?revision=2&view=markup , title = Version 1.0 license , website = anonscm.debian.org , access-date = 2016-06-19 , archive-url = https://web.archive.org/web/20130602181949/http://anonscm.debian.org/viewvc/pkg-wmaker/trunk/COPYING.WTFPL?revision=2&view=markup , archive-date = 2013-06-02 , url-status = dead {{cite web , url = http://www.blackducksoftware.com/resources/data/top-20-licenses , title = Top 20 licenses , publisher = Black Duck Software , date = 31 May 2016 , access-date = 2016-05-31 , archive-url = https://web.archive.org/web/20160719043600/https://www.blackducksoftware.com/top-open-source-licenses , archive-date = 2016-07-19 {{cite web , url = https://creativecommons.org/weblog/2009/03/11/13304 , title = 11/17: Lulan Artisans Textile Competition , date = 18 June 2009 {{cite web , url = https://rd-alliance.org/sites/default/files/cc0-analysis-kreuzer.pdf , title = Validity of the Creative Commons Zero 1.0 Universal Public Domain Dedication and its usability for bibliographic metadata from the perspective of German Copyright Law , author = Till Kreutzer {{cite web , url = https://creativecommons.org/weblog/entry/27081 , title = Using CC0 for public domain software , date = 15 April 2011 , publisher =

, access-date = 2011-05-10 {{cite web , url = https://www.gnu.org/licenses/license-list.html , title = Various Licenses and Comments about Them , publisher =

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 Computer hardware, computing dev ...

, access-date = 2015-04-04 {{cite web , url = http://opendefinition.org/licenses/ , title = licenses , work = The Open Definition {{cite web , url = https://blog.creativecommons.org/2013/12/27/creative-commons-4-0-by-and-by-sa-licenses-approved-conformant-with-the-open-definition/ , title = Creative Commons 4.0 BY and BY-SA licenses approved conformant with the Open Definition , author = Timothy Vollmer , website = creativecommons.org , date = 27 December 2013 {{cite web , url = https://anweshadas.in/software-licenses-in-fedora-ecosystem/ , title = Software Licenses in Fedora Ecosystem , date = 22 June 2016 , access-date = 2016-06-27 , website = anweshadas.in , author = Anwesha Das {{cite web , url = http://ostatic.com/blog/the-unlicense-a-license-for-no-license , title = The Unlicense: A License for No License , website = ostatic.com , author = Joe Brockmeier , date = 2010 , url-status = dead , archive-url = https://web.archive.org/web/20160324154539/http://ostatic.com/blog/the-unlicense-a-license-for-no-license , archive-date = 2016-03-24 {{cite web , url = http://unlicense.org , title = The Unlicense , website = unlicense.org , access-date = 2020-05-12 , archive-url = https://web.archive.org/web/20180708180735/http://unlicense.org/ , archive-date = 2018-07-08 , url-status = dead {{cite web , url = https://github.com/blog/1964-license-usage-on-github-com , title = Open source license usage on GitHub.com , date = 9 March 2015 , author = Ben Balter , access-date = 2015-11-21 , website = github.com Permissive software licenses Public domain Public copyright licenses Terms of service