Any examples of libraries linking to UE4?


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.