It's not a lot of use without any scripting support. And no, I'm not privy to the details of any financial arrangements between Unity Technologies and XamarinUnity uses Mono to support scripting, which includes UnityScript, Boo or C#, Unity itself (runtime) is not written in C#, it's native and IIRC it's written in C++. How is that 'based on Mono'? By the way, do you know if the Mono devs get even a penny out of Unity's use of it as a scripting engine?
Anything less than majority is irrelevant?By it becoming the dominant development platform on mobile.