No, SCO was found in 2002, from Candera Software who was a Linux distributor [0]. How could Microsoft in 1980s own a company that wasn’t founded until 2002?

They later filed for bankruptcy in 2007.

[0] https://en.m.wikipedia.org/wiki/SCO_Group

Not sure where yours is coming from, if we look at [20] it makes no such claim.

https://web.archive.org/web/20061105100939/http://www.inform...

Owning stock, on its own, is not the same as buying a company