I'm looking into creating a new Joomla 1.5/UBB.threads bridge.
Since Joomla has a plugin system with event dispatches on everything necessary (login/logout/storing users/etc) it should be a breeze.
I'm guessing the JFusion component could be used as well, but it seems to be a lot more work.
I just need to read up on how UBB.threads cookie handling works nowadays. Hopefully I can copy the code from my old bridges.