How come Linux replaced Unix? What happened to proprietary Unix?

The personal histories involved are highly relevant and they are one of the things that get forgotten in boring grey corporate histories. Bill Gates didn't get lucky: he got a leg up from mum & dad, and was nasty and rapacious and fast, and clawed his way to industry dominance. On the way he climbed over Gary Kildall of Digital Research and largely obliterated DR. Ray Noorda of Novell was the big…