Actually, https://github.com/Astn/JSON-RPC.NET is a stand alone json rpc server. It just happens to have a plugin for ASP.net.
There is no dependency in ASP.net or IIS.
Check out the documentation on running a console server at that link you posted.
There is also a discussion there about hosting that server over raw sockets.
-- Edited url to github instead of codeplex --