Complex sentence: The U.S. copyright of the film was not renewed after its first term expired in 1968, although because it is a derivative work from a play that is still under U.S. copyright, it cannot be said to be in the public domain.
Split into simpler sentences: The U.S. copyright of the film was not renewed after its first term expired in 1968. However, because it is a derivative work from a play that is still under U.S. copyright, it is not deemed to be in the public domain.