Yes. Would be reasonably easy actually particularly given that the hardware is pretty well known. Still a fair bit of work though. When I helped with porting it to the Toshiba Gigabeat (which already ran Linux on an ARM9) I had the idea of running it as an application under Linux.

Instead they created it as a standalone application and it really does work well - so much better than the original rubbish that it came with. Rockbox is still missing some empeg features though.