I'm not sure about american law but in EU (at least Sweden) you def get copyright to detivative work even if you don't have a license. If I create a derivative work based on Harry Potter the result will be that I have copyright to the derivative work BUT not to Harry Potter (I wish) so while I own the rights to my work I can't produce (etc) the work (at least not in a commerical capacity) because JK rowling owns the Harry Potter rights. However JK does not have the right to use my derivative work without a license from me.

A maybe more clear example is music. Songwriting is covered by copywrite. Singing is also covered by copywrite. If A writes a song and B sings the song without A:s premission it can be copyright infringment. However, A can not take a recording of B:s song and copy and sell it without B:s consent because B has the copyright to the performance (even if the performance was a copywright infringment).