and run their own platform and Bill Gates is able to sell DOS to Steve Jobs?
How would the IT world look today?
Apple doesn't need DOS, for starters, since it has (perhaps you've heard of this?) MacOS (as well as Lisa and the Apple II).
Hmm. Well that doesn't sink Microsoft (they're working on Word and Excel, and of course Windows is still possible) but it does matter for IBM—how does an alternate OS turn out?
Are IBM compatible's still doable? If so, then IBM/OS probably winds up dominating albeit without Microsoft along I can't imagine IBM/OS being anywhere near as successful as MS-DOS/Windows (IBM was pretty incompetent in the 1980s—witness their contract with Microsoft—despite flashes of brilliance like the PC or the POWER CPU design).
If Apple and IBM refuse to let their machines be cloned (and, unlike OTL, IBM can enforce that), that opens up a new hole for Windows (albeit less business successful without IBM) and the Amiga.
Potentially NeXTSTEP and BeOS as well, assuming they happen.
Actually OpenStep might be more important or even vital to the computing world if the OS market winds up fragmented.
The CPU guys? Intel, Sun, Motorola, and of course IBM. What happens there?
Intel takes a hit, maybe Motorola does better, maybe Sun can sell a consumer SPARC (like IBM's consumer POWER, the PowerPC), maybe somebody else gets in the game bigger—DEC Alpha or MIPS or PA-RISC or whatever.