Or if you're worried about the licensing of Singularity, Singh and others, check out MOSA (http://www.mosa-project.org/) which tried to bring back SharpOS and EnsembleOS together (both inactive now unless something changed lately), or jNode (or many others I missed probably). They should be all in a runnable state (even if very limited).

There's been a lot of this stuff happening around. There are many paths - which unfortunately cannot include many of the existing native (unsafe) solutions.