Any examples of libraries linking to UE4?

Hi,

I’ve so far only found example programs (like SlateViewer and UnrealPak) which link to UE4, but no libraries.
Is it possible to create a library which uses some functionality from UE4? This way it would be possible to create C# frontends for stuff which uses the Unreal Engine runtime. For example, this could be useful for a C# version of UnrealPak.