<< There is a case that borders on this. Namely, the DR-DOS. Basically, DR-DOS was a competitor to MS-DOS. DR-DOS was superior in many ways to MS-DOS, and it had things like disk-compressor and memory-manager (you know, to maximise the amount of bree base RAM) years before MS-DOS got 'em. In order to harm DR-DOS, MS deliberatly Modified Windows 3.1 in such way that it checked what version of DOS it was running on. If it was DR-DOS, it would display error-messages. The truth was that there was no reason why Windows wouldn't run on DR-DOS, MS just made sure that it wouldn't Caldera then sued MS over that issue, and MS settled out of court. >>
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. MS developed 3.x using MS-DOS as the platform, so why should they support DR-DOS? 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? It's still "unix", 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.