Works in the public domain are those whose intellectual property rights have expired,[1] have been forfeited,[2] or are inapplicable. https://en.wikipedia.org/wiki/Public\_domain

A public license or public copyright license is a license by which a licensor can grant additional copyright permissions to licensees and in which either the licensees or both the licensees and licensors are unlimited https://en.wikipedia.org/wiki/Public\_copyright\_license

Copyleft (a play on the word copyright) is the practice of using copyright law to offer the right to distribute copies and modified versions of a work and requiring that the same rights be preserved in modified versions of the work. https://en.wikipedia.org/wiki/Copyleft

An open-source license is a type of license for computer software and other products that allows the source code, blueprint or design to be used, modified and/or shared under defined terms and conditions. https://en.wikipedia.org/wiki/Open-source\_license

A Creative Commons (CC) license is one of several public copyright licenses that enable the free distribution of an otherwise copyrighted work. https://en.wikipedia.org/wiki/Creative\_Commons\_license

The Open Database License (ODbL) is a “Share Alike” license agreement intended to allow users to freely share, modify, and use a database while maintaining this same freedom for others. https://en.wikipedia.org/wiki/Open\_Database\_License

A permissive free software licence is a class of free software licence with minimal requirements about how the software can be redistributed. Such licenses therefore make no guarantee that future generations of the software will remain free. https://en.wikipedia.org/wiki/Permissive\_free\_software\_licence