If that seems absurd, consider how few people were programming back then and how fundamental and basic the APIs were. It’s worse than the patent mess. At least patents expire in 20 years! Copyright for those 1970s APIs will belong to my heirs for 50 years after I die! (see the Mickey Mouse law [2]).
[1] https://en.m.wikipedia.org/wiki/9_track_tape
[2] https://www.google.com/search?q=mickey+mouse+copyright+law&i...