Public copyright licenses

A public license or public copyright license is a license by which a copyright holder as licensor can grant additional copyright permissions to any and all persons in the general public as licensees. By applying a public license to a work, provided that the licensees obey the terms and conditions of the license, copyright holders give permission for others to copy or change their work in ways that would otherwise infringe copyright law.

Some public licenses, such as the GNU GPL and the CC BY-SA, are also considered free or open copyright licenses. However, other public licenses like the CC BY-NC are not open licenses, because they contain restrictions on commercial or other types of use.

Public copyright licenses do not limit their licensees. In other words, any person can take advantage of the license. The former Creative Commons (CC) Developing Nations License was not a public copyright license, because it limited licensees to those in developing nations. Current Creative Commons licenses are explicitly identified as public licenses. Any person can apply a CC license to their work, and any person can take advantage of the license to use the licensed work according to the terms and conditions of the relevant license.

According to the Open Knowledge Foundation, a public copyright license does not limit licensors either. Under this definition, license contract texts specific to a single licensor (like the UK government’s Open Government License, which would have to be edited to be used by other licensors) are not considered public copyright licenses, although they may qualify as open licenses.

Some organisations approve public copyright licenses that meet certain criteria, in particular being free or open licenses. The Free Software Foundation keeps a list of FSF-approved software licenses and free documentation licenses. The Open Source Initiative keeps a similar list of OSI-approved software licenses. The Open Knowledge Foundation has a list of OKFN-approved licenses for content and data licensing.

The implied license imposed by the Berne Convention, and the public domain (the CC0 license as waiver), are the references for any other public license. Considering all cultural works, as in the Open Definition, the four freedoms summarizes the main differences:

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