The Share Alike clause of the Creative Commons open content copyright? license? suite? requires that everyone who improves a work must release the improvements to all others who satisfy other terms of the license.

A copyleft? or free software license is "Share Alike to everyone" which means that there are no restrictions on field of use? and no restrictions on who may use? the licensed material. In Creative Commons the CC-by-sa license may be describe as "copyleft" and is roughly equivalent to similar licences like the GFDL. The CC-by-nc-sa is not copyleft as it does not require releasing permission for commercial use. The Terms of Use of the Living Platform use this latter license.

This is a cite link referring to a definitive evidence/source/authority An official discussion on the implications of this clause are at en: creativecommons: Share_Alike.