That would be because Microsoft sold the rights to Xenix to SCO -- at that time about two hackers and their hot tub in downtown Santa Cruz -- in return for 30%

That would be because Microsoft sold the rights to Xenix to SCO -- at that time about two hackers and their hot tub in downtown Santa Cruz -- in return for 30% of the shares in the (then private) company. That was in the mid-to-late 80s (before my time there).