Comment by sgjohnson

Funnily enough, they had no certification and weren’t compliant in 10.0-10.3 days, so what they were doing was trademark infringement, hence the lawsuit from the Open Group. 10.4 was the first compliant version. And oh boy they really milked it for several years afterwards.

https://www.quora.com/What-goes-into-making-an-OS-to-be-Unix...