Creative Commons is a non-profit organization, best known for their publicly reusable licenses, that promote the legal sharing and improvement on creative works. The licenses used do not replace copyright, but rather place a series of "terms-and conditions" that the author may impose on their creative works, instead of using a generic "all rights reserved" policy, resulting in a low-overhead, simple to use license that can be exported almost anywhere. This also differs from the category of public domain in that the author reserves some rights to himself by granting such a license.
Terms and conditions
Various forms of the Creative Commons License are often used. The most common conditions that granting authors place on Creative Commons-licensed work include the following conditions, or combinations thereof:
- Attribution: users must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. (For example, it may be reasonable to satisfy the conditions by providing a URL or hyperlink to a resource that includes the required information.)
- Share-Alike: If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.
- Adapt — remix, transform, and build upon the material for any purpose, even commercially.
- The licensor cannot revoke these freedoms as long as you follow the license terms.
- No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.
CC-BY-SA is a license of more than 3,100 words that exists in several different versions (e.g., "3.0"). It was adopted by Wikipedia in 2009 to replace the GFDL, the even more complicated license that Wikipedia was previously using.
Attribution-ShareAlike 3.0 Unported FULL LICENCE: 
The new Attribution-ShareAlike 4.0 International FULL LICENCE: 
The Creative Commons site provides links to repositories of Creative Commons-licensed works. In addition, the multimedia sharing service Flickr advises its users on how to license their work under Creative Commons, if they so desire.
- Creative Commons official site