C# x64 operating system programming with the .NET native ahead-of-time compilation technology.
ComWrappers required to run NativeAOT and WinForms
A UEFI loader and OS kernel written in C# and compiled to native code with CoreRT.
Now open source and free and no support and no updates ;)
A port to immutable and functional F# from the original Java implementation by j.tarbell (http://www.complexification.net/gallery/machines/substrate/)
Development server suitable for embedding in dotnet / corert applications.