There is one DC emulator that runs a commerical game, one game. The game is Namco Museum. But this emulator is private and has not been released. No other working DC emulators exist at this time. Sorry.
Also, it has source code and explinations of what the authors did to write their Emu for the DC, right now i have the private code for DreamSNES that i am optimizing for my own use... But anyways, yes, if there is going to be news on the DC emulators, thats where it will be first... Even before its on the authors webpages...