To be fair, in earlier times it wasn't clear if software was copyrightable. In the US the Copyright Act of 1976, which became effective on January 1, 1978, clea

To be fair, in earlier times it wasn't clear if software was copyrightable. In the US the Copyright Act of 1976, which became effective on January 1, 1978, clearly stated that Congress intended software to be copyrightable; before that there were many questions. So before that, in the US many considered any source code distribution as equivalent to a permissive license. Unix v6 source was well distributed, but the Lyons book (with Unix source code)) was only distributed as Samizdat for years because it wasn't clear it was legal.