Similar, more mature projects based around other languages:
Erlang: http://erlangonxen.org
C#: http://en.wikipedia.org/wiki/Cosmos_(operating_system)
C#: http://en.wikipedia.org/wiki/SharpOS_(operating_system)
- House http://en.wikipedia.org/wiki/House_(operating_system)
- HOP (House parent) http://lambda-the-ultimate.org/node/299 (topic recurse on jnode and others)