[pauldbau]

The key paragraph from the post RE:Mono is:

"we’ll make .NET Core great for Windows, Linux and Mac OSX. This also enables the Mono community to innovate on top of the leaner .NET Core stack as well as taking it to environments that Microsoft isn’t interested in."

Seems like a pretty clear split - MS will cover the server-side + Win UIs, while Xamarin handles the other plats (IOS, Android, PS4 etc).

This plays to the strengths of both companies, and I would not be surprised if MS has some security in place - e.g. some kind of first option to buy Xamarin should another suitor come calling.