Didn’t Microsoft somehow ruin Dr DOS? Not technically, but didn’t they sue them or something? Which would mean this is the same issue, 40 years later. Yes, I was there on the 80s, but I had a Commodore 64. We did use GEOS, if that counts. I was not present for the 70s.

> Didn’t Microsoft somehow ruin Dr DOS?

They added some obfuscated code to Windows 3.1 that made it refuse to run on DR-DOS. https://en.wikipedia.org/wiki/AARD_code