MS-DOS initially was developed as a joint product between IBM and Microsoft and had two names: PC-DOS and MS-DOS. PC-DOS/MS-DOS was hardly the first operating system for microcomputers. It wasn't even the second or the third. It was just one of many similar systems that were available all competing for a share of the OS market for microcomputers (not just PCs) in the 1970's and 1980's. PC-DOS and MS-DOS looked similar to CP/M-86 which was derived from CP/M, but had a major difference that MS and IBM came up with, the File Allocation Table. CP/M was arguably the first microcomputer OS, although it borrowed extensively from several mini-computer operating systems developed by Digital Equipment Co. in the 1960's and the 1970's. (e.g. RSTS/E for DEC's PDP-11 mini-computer.)
The GUI as we know it today (icons, windows, moving and clicking with a mouse, etc., etc.) was invented at SRI and then Xerox's PARC in the late 1960's and early 1970's. The roots of GUIs go back to about 1945. A guy by the name of Jobs then brought in a lot PARC people for GUI development as Job's company (Apple) was a creating a new computer called the Lisa. The Lisa flopped, but the idea of the GUI did catch on. Apple released refined GUIs on several other machines, up to and including the MacIntosh Model 1. From that initial Mac on out, Apple used the GUI exclusively.
IBM and Microsoft then decided to develop their own GUI, and get rid of PC-DOS and MS-DOS. The new product was called OS/2 and was released in 1987. About 1990, MS and IBM ended their partnership on GUI development. IBM retained the OS/2 operating system, while MS developed Windows 1 and 2. MS eventually released Windows 3 to the public.
That seems to be an awful like stealing. If someone can't afford to buy it, they should do without it.
Even if MS had stolen the products as you claim -which is demonstratively false-, how is it right to release the code to a third party? By any normal application of law, any relief for wrongdoing should go to the original program developers or the heirs, not a third party.
As to 'turning my back on an open source alternative', you misunderstand me. Personally, I use a lot of open source products. Some of them, such as BackTrack, I love (just as I love some MS products). Others are pure crap (also, just like some MS products), and if I never use them again, it will be too soon (ditto on the bad MS programs). It's just that in my opinion, no government should ever screw around with markets, and that ideas such as "monopolies" are little more that governments trying to exert control over things that they should never get near, such as economics and markets. So it's not turning my back on open source, it's that I'm very uncomfortable with any government sticking their noses into areas they don't belong.