2007-06-21, http://tirania.org/blog/archive/2007/Jun-21.html
we believe that Silverlight is a fantastic development platform, and its .NET-based version is incredibly
interesting and as Linux/Unix users we wanted to both get access to content produced with
it and to use Linux as our developer platform for Silverlight-powered web sites.
2014-06-21, Announcement
of Xamarin.Forms (Xamarin (allowing cross-platform development in C#) became a Microsoft partner and shortly after that, Xamarin Forms came along.)
You can check the license included with the Xamarin.Forms NuGet for further details.