Blu-ray Menu support is in development, just not by me.
Also, Java menus are not supported at all yet, which means only 30-40% of all discs work with it right now (and a few of the non-Java discs still fail, as well).
Integrating this into a player is still quite a lot of work, its not simple plug'n'play. Its probably alot easier to do it in a standalone player without DirectShow in between, too.
Its generally not in any shape to consider it "stable", but if JRiver is interested i could forward the required information/contacts.