It seems the tags derivative-works, derived-works and derivatives are all used for the same thing. Should the latter two be superseded with the first? Should either of the first two be retained as redirects, or should they just be burniated?
Let's keep derivative-works and make the other two synonyms.
It is the clearest and searchable out of the three. The other two can still function as redirects. If something gets tagged with a synonym, the master tag gets shown anyway.