CC0-1.0 is a public-domain dedication. The author waives, to the fullest extent permitted by applicable law, all copyright and related rights — and in jurisdictions where waiver is not possible, grants an equivalent unconditional licence.
CC0 does not grant patent or trademark rights. For software, the FSF considers CC0 free and GPL-compatible, but OSI has not formally approved it.
For content, media, and data, CC0 is the most permissive option. For software specifically, many projects prefer MIT or the Unlicense.
How to apply
Add a LICENSE file with the full CC0 dedication. A one-line attribution in README is courteous but not required.
Full license text
Creative Commons Legal Code
CC0 1.0 Universal
CREATIVE COMMONS CORPORATION IS NOT A LAW FIRM AND DOES NOT PROVIDE
LEGAL SERVICES. DISTRIBUTION OF THIS DOCUMENT DOES NOT CREATE AN
ATTORNEY-CLIENT RELATIONSHIP. CREATIVE COMMONS PROVIDES THIS
INFORMATION ON AN "AS-IS" BASIS. CREATIVE COMMONS MAKES NO WARRANTIES
REGARDING THE USE OF THIS DOCUMENT OR THE INFORMATION OR WORKS
PROVIDED HEREUNDER, AND DISCLAIMS LIABILITY FOR DAMAGES RESULTING FROM
THE USE OF THIS DOCUMENT OR THE INFORMATION OR WORKS PROVIDED
HEREUNDER.
Statement of Purpose
The laws of most jurisdictions throughout the world automatically confer
exclusive Copyright and Related Rights (defined below) upon the creator
and subsequent owner(s) (each and all, an "owner") of an original work of
authorship and/or a database (each, a "Work").
Certain owners wish to permanently relinquish those rights to a Work for
the purpose of contributing to a commons of creative, cultural and
scientific works ("Commons") that the public can reliably and without
fear of later claims of infringement build upon, modify, incorporate in
other works, reuse and redistribute as freely as possible in any form
whatsoever and for any purposes, including without limitation commercial
purposes. These owners may contribute to the Commons to promote the
ideal of a free culture and the further production of creative, cultural
and scientific works, or to gain reputation or greater distribution for
their Work in part through the use and efforts of others.
For these and/or other purposes and motivations, and without any
expectation of additional consideration or compensation, the person
associating CC0 with a Work (the "Affirmer"), to the extent that he or
she is an owner of Copyright and Related Rights in the Work, voluntarily
elects to apply CC0 to the Work and publicly distribute the Work under
its terms, with knowledge of his or her Copyright and Related Rights in
the Work and the meaning and intended legal effect of CC0 on those
rights.
… this text is abbreviated.
For the complete license text, see
https://creativecommons.org/publicdomain/zero/1.0/legalcode
Raw text also available at /license-texts/CC0-1.0.txt — handy for curl.