Share-alike is a descriptive term used in the Creative Commons project for copyright licenses which include certain copyleft provisions. The specific definition used by Creative Commons is that "If you alter, transform, or build upon this work, you may distribute the resulting work only under the same, similar or a compatible license." However, generic variations of share-alike licenses define free software and open content. The term copyleft has been used since the 80s to describe these terms by the free software community, but only as far as free licenses are concerned.