Why should I use the share-alike (SA) or copyleft term?
The decision of whether or not to use the share-alike (SA) term, also known as copyleft (such as with the GNU FDL), is a personal one, based on the priorities of the author. If an author’s primary purpose in creating open educational resources is for it to be used as widely, freely, and creatively as possible, then using CC-BY is the better choice. CC-BY allows for a variety of motivations, including the possibility of commercial success, to drive users to adapt and re-purpose their materials. In most cases, it seems likely that the derived materials will remain openly available, but even if they do not, there is nothing preventing someone from using the original source materials for their own needs, regardless of what others have done. If an author’s primary purpose in creating open educational resources is for that material to never leave the educational commons, such as it is, then you may want to apply the SA term. In this case, the possibilities for viable commercial derivatives,
