Oh, I know that.
I just don't take it seriously. If someone asks a question like, "What specs is Bill Gates computer", probably you'll get back a really detailed answer from someone who just makes up random stuff that he would like Bill Gates to be into. That's what I'm saying.
I actually know, from an interview that I read a few years ago, that his entire home security system runs on the Windows OS. He has lights, cameras, temp settings, and everything running through about 30 computers that are connected together to form a matrix of computers. I somehow doubt that he would be using Ubuntu as his primary system, because of that, because you can't really run as many programs on Linux. It's a geek's dream, and I think it's quite possible that Gates uses both, but not as his primary. He would be using the system he designed himself.
EDIT: The interview was in Time magazine, I believe. Or maybe Computer World. I can't remember, I was in a doctor's office, and the interview caught my eye. Probably 2010 or 2011.
More information:
http://seattle.curbed.com/archives/2013/01/bill-gates-medina-mansion.php
15. Anyone in the house can "call up" a favorite painting or photograph on $80,000 worth of combination TV-computer screens that is run by several $150,000 computer-storage devices.
Somehow, I don't believe the operating system is Linux, unless it is very tightly controlled and spec oriented away from Ubuntu.