It's not really a question of originality. It's a matter of using someone else's work without permission. Fair use law recognizes that there are circumstances where that is legitimate, and lays out certain guidelines. This didn't pass. It's derivative within the meaning of copyright law. It's quite possible for a new work (say a movie adaptation of a book to give a common example) to be very different from the original and still be an adaptation that is not covered by fair use.I'm on the fence regarding wether or not his work can be considered original or not.
There's a good discussion of the case over here: