@Don, cannot write an operating system?
> They are an enemy of Microsoft, and like every other organization that cannot write an operating system themselves, they ported UNIX.
I'm afraid you're showing your limited background there. IBM wrote, from scratch, rather a lot of operating systems back when operating systems were terra incognita (and their purpose and functions still being defined) and it gave them away up to 1980 or so, in source code (assembler), under the rubric of "Systems Control Programs (SCP) -- necessary to make the hardware work", since they were a hardware company.
I agree it's unfortunate that the one that had legs was OS/360 VS2 (which morphed into MVS or whatever it's called nowadays) -- VM/370 CMS was much more fun and was the first "Personal Computing" experience for many employees of large organisations (at least, of large organisations that weren't engineering firms).