The download page for the latest version includes this question from another user:
Is it a winamp plugin or a Keyboard plugin?The developer's answer might explain why it won't work with MusicBee:
Well actually it is neither, hence the name “App”. Just unzip to a folder of your choice and start it.Maybe there's some hokery pokery going on to make it work with Winamp and Media Monkey, despite not being a plugin.
You could email the developer and ask, or even better ask them to add support for MusicBee.
Otherwise, there's another G15 plugin on the Winamp site you could try:
http://www.winamp.com/plugin/g15-lcd-display/221692Without one of these fancy keyboards to practice with, I can't offer much more. Sorry.
Bee excellent to each other...