Creative Commons Share Alike

Creative Commons Share Alike licenses are:

• CC-sa
• CC-nc-sa - used for GetWiki code
• CC-by-sa - used for Wikitravel open content
• etc.

Like all Share Alike licenses anyone who extends and improves the material must re-release it under the same license exactly with no variation in terms. This is similar to Share Alike provisions in GFDL and GPL. Note: the definition of open source explicitly does NOT require share-alike terms so it is simply wrong to assume that open content necessarily is open source.