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 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. 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 disclaimer. In 2016, according to Black Duck Software, the WTFPL was used by less than 1% of FOSS projects. In 2009, Creative Commons released CC0, which was created for compatibility with jurisdictions where dedicating to public domain is problematic, such as continental Europe. This is achieved by a public-domain waiver statement and a fall-back all-permissive license, for cases where the waiver is not valid. The Free Software Foundation 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.