Permissive free software licences are free software licences for a copyrighted work that offer many of the same freedoms as releasing a work to the public domain. In contrast, copyleft licences like the GNU General Public License require copies and derivatives of the source code to be made available on terms no more restrictive than those of the original licence.
Comparison to public domainEdit
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, such licences are not actually equivalent to releasing a work into the public domain, so such a term can be considered a misnomer.
Some permissive free software licences contain clauses that require advertising materials to credit the copyright holder. Licences with an advertising clause include the 4-clause BSD license, the PHP License, and the OpenSSL Licence. These licences, although they are permissive free software licences, are incompatible with the GNU General Public License.
See also Edit
- Free software licence
- Comparison of free software licences
- List of FSF approved software licences
- List of OSI approved software licences
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