You could conceivably compile perl or python, but I doubt that it's worth your while. If bash won't do what you want (as much as I dislike it, it's reasonably powerful), yes, you're pretty much stuck compiling a binary, though it need not be written in C, necessarily.

I seem to remember someone compiling lame for the empeg, but it's not fast and it doesn't really have anywhere to write output to. You might be able to stream data to the audio device, but that's hardly the type of output lame would produce.

You should be wary of some of the idiosyncrasies of the empeg's serial port before you start down that road. Someone else is probably more versed in that area than I am.