I'm pretty sure the likes of Dell, Lenovo, Asus, NVidia and AMD would simply fork Windows for their own usage, and stop paying licensing... that would mean huge gaps in Microsoft's income... bad idea.

Opening .Net up, I feel is for a couple reasons. First, keeping developer mindshare. Second, Keeping Azure as a first-class platform for deploying .Net code. Third, reducing costs within Azure division that are tied to Windows' licensing. The fact that it's probably the right thing to do, is probably farther down the list.