Hmm, seems theres a tad of confusion here, there is indeed a great server from Ouka , but what Josh is referring to is the Ouka Chat Client 2 (OCC2) .
This can be obtained from here http://www.interq.or.jp/orange/satosi/ChatClient2E_100b_2005_04_26_2200.zip
This client is now a standalone client unlike the previous version (100a) as Ouka is sort of re-inventing the wheel, but its his own build and that means he fully understands its operation, and any improvements will arrive faster because of this.
The interface is similar to a Nushichat client and the right click menu is currently only enabled for RCMS/Ouka rooms .
All in all a nice peice of work, so Josh, my advice is to upgrade to this version.