EGA Trek for DOS got a sternly-worded letter. Later versions had “USS Lexington” fighting the “Mongols”, rather than the Enterprise and Klingons.

A niche mainframe game from 1971, and its successors like BSD Trek, were flying way below the radar of any lawyers back then. Even through the early/mid-80's, developers took great liberties with IP and largely got away with it. (Regard the "Prisoner" game from 1980 [1].)

I remember buying a C64 port of Trek off the shelf at Target in the mid-80s which was clearly not licensed. I don't think anyone could get away with that today. :)

[1] https://en.wikipedia.org/wiki/The_Prisoner_(video_game)#Diff...