This begs the question: if the original movie was copyrighted, how does releasing the same movie with a different title make the new re-release considered a new (not-yet-copyrighted) work? I thought the copyright protection of the original would extend to the renamed version, since they're 99.99% the same. Theoretically, does changing even one frame necessitate a new copyright?
Today things are much easier, if you create something it is copyright. If you want to sue you need to register, but you can register at anytime. If you register you can sue for triple damages for anything that happens after you register, but you can still get damages for things that happened before your register. (The above is my understanding of the law, but I'm not a lawyer)
Software can simultaneously be covered by copyright, trade secret and patents. The patents have to disclose some info, of course.
Even when distributed you can distribute just the binary, and keep the source a trade secret.
This has not been true for a very long time.
Now, fixing a creative work in a tangible medium is all that's required. When does the copyright expire? Nobody will know, because there's no year of publication listed, and no author listed to find out when they die. (Even if there is an author listed by name, maybe it was me; maybe it was the Pulitzer Prize winning author)