Comment by throwaway150 4 hours ago
> If you didn't mention the license, it was in public domain.
I don't think this has ever been the case. If a license is not mentioned, it is always "All rights reserved" by the authors of the project, by the Berne convention (1886).
Wow. I didn't know that. Looks like this is a very US thing. I looked up now and TIL that US adopted the Berne convention as late as 1989. I'm surprised. So this movie released in 1966 didn't have default "all rights reserved" due to Berne convention. But most European countries, like 80%, had adopted the Berne convention by 1925. So when software was developed in Europe they automatically got "all rights reserved".
I believe that was a forgotten renewal of copyright status.
However, the United States did not join the Berne Convention until 1988, and prior to 1978 it did not automatically grant federal copyright when a work was created; instead you had to register your work with the Copyright Office in order to receive federal protection. There were also some state-level protections at the time that did not require registration, but apparently they weren't very strong.