The latest mono master builds csc "dim" version. It will be installed as
$prefix/lib/mono/4.5/dim/csc.exe etc.
This project is to build a nuget package that simplifies use of the new
compiler. Add xamarin.android.csc.dim package, and set your C# language
version to the "latest", and you're good to go.
Apache License 2.0 is applied as it contains Roslyn binaries.