Hendrik Iben wrote a modplug plugin which can be downloaded from http://www.tzi.de/~hiben/moc/. It uses libmodplug and supports various formats like .mod, .ux etc. It will be added in the next release (2.5.x line).
I also want to inform that I have a new job which in conjunction with my other activities prevents me from doing MOC development, I don't have enough free time for that :(. It means that you should not expect any new feature-rich release (2.5.0). What I want to do is to fix some bugs that are listed in my TODO file (about 6-10, some are unconfirmed) and make a bugfix version, but even this little release should not be expected soon. This is the moment when you (free software community) can help, if you want a new feature in MOC, don't ask for it, you must do it yourself, the modplug plugin is a good example.
I hope this situation is temporary and MOC development will continue somehow.