[JKCalhoun]

Thank you for that. I was going to post something similar.

What the Apple engineers did was take obvious inspiration from what they saw at PARC but then ended up going in a different direction when they actually had to both implement it and make it workable as an OS. The overlapping windows is the most oft-cited innovation they came up with but there were many other perhaps more subtle ones.

The impression I have though is then that Gates basically copied Apple engineering, not PARC.