What do you mean by "derivative works are exempt from copyright claims" ? Standard language is copyright law around the world includes essentially "The owner o

What do you mean by "derivative works are exempt from copyright claims" ? Standard language is copyright law around the world includes essentially "The owner of copyright has the exclusive rights to do and to authorize derivative works based upon the copyrighted work", there are various more specific details that may apply and change that, but the default scenario is that derivative works definitely require blessing from the copyright owner.