Hello.
The MCIO plugin was developed by JHC (Jonathan). The December 2002 version you have is the most current version (or, at least it was a few weeks ago when I asked JHC). It generally should not need to change whenever JRiver adds new Automation interfaces.
It is a great plugin - I use it all the time to access MC via JavaScripted web pages controled by Girder for on-screen menus via IR remote control. However, as of MC 9.1.240, you no longer need MCIO to control MediaCenter from out-of-process, but you can do it directly under the Automation name "MediaJukebox Application". In my experience, however, MCIO is about twice as fast as accessing directly (but why?).
Regards,
Soundman