<< I'm not entirely familiar w/ this, so I can't comment on it. Windows 3.x was an operating environment for MS-DOS. It was not an operating environment for all DOS-based platforms. There may have been architectural reasons as to why Windows 3.x would not run on DR-DOS. >>
But there wasn't. DR-DOS was 100% compatible with MS-DOS. And to my knowledge, as the case progressed, it was found out that Win3.1 deliberatly checked the version of DOS it was running on. If it was DR-DOS, it would display error-messages.
Kinda like:
If (DOS == DR-DOS)
Then
Display.error.messages
Sorry, I ain't no programmer 😱
<< MS developed 3.x using MS-DOS as the platform, so why should they support DR-DOS? >>
No, they are not required to support it, but they are not allowed to deliberatly sabotage it either. That's what they did, that's why they were sued and that's why MS settled.
<< In those days operating environments were tightly coupled to the underlying platform. If you install a Linux distro, you don't go download a binary for another architecture and expect it to run do you? >>
Of course it wouldn't work out of the box, but that doesn't mean that other UNIX-manufacturers deliberatly try to sabotage Linux.
<< It's still "unix", >>
Linux is not UNIX. It's UNIX-like, but it's not UNIX. Some call complete Linux-OS GNU/Linux. "GNU" Stands for "GNU's Not Unix". But I digress.
<< but that doesn't mean that one company should (or can) support the execution of their work on competing platforms, and indeed, that isn't the case. >>
Nobody is forcing MS to support DR-DOS. The case was about deliberate sabotaging of competing product.