Creative Commons

Creative Commons is a non-profit (under the US tax code, a 501(c)(3)) organisation that was created by Lawrence Lessig and is best known for creating licenses which can be used by creators of content to make it copyleft - that is, subject to copyright but under a looser set of rules that encourage reuse. This makes it similar to the sort of licenses used for free and open source software such as the GNU General Public Licenses and the MIT/BSD licenses, but designed for creative works such as written texts, photographs and visual artworks, films, videos, musical scores, musical recordings and multimedia.

Creative Commons licenses are used widely by bloggers, wikis (including Citizendium and Wikipedia as well as many others) and photographers on sites like Flickr.