Sounds like you're confusing Microsoft with Apple. And, OSX actually IS BSD Unix.
No confusion at all, it was Apple that visited the PARC lab on that fateful day.
Like millions of others, I could be easily confused by all the permutations of Unix, which I consider a difference without a distinction.
Bruce Horn's Statement on the source of the Mac user interface.
Jeff Raskin's Commentary on the creation of the Mac interface.
When asked about Apple's "theft" of the Parc ideas, Steve Wozniak stated:
"Steve Jobs made the case to Xerox PARC execs directly that they had great technology but that Apple knew how to make it affordable enough to change the world. This was very open. In the end, Xerox got a large block of Apple stock for sharing the technology. That's not stealing outright.
"Apple didn't get any stock from Microsoft. Nor was Apple dealt with openly in this area by Microsoft. " - Source Woz.org
Your characterization of the Parc visit as "lifting" the GUI is untrue.