Other people have reported that it is easy to add a USB socket to the MusicPal. As its internal memory is very limited I think this will be useful for software development, so decided to give it a try.
Sure enough, you can open the case easily by removing three screws and pulling the knobs off the front panel. There are clips on the right hand side of the front panel, so you have to start to open the case from the left (speaker) side and pull the front panel to the left a bit to release the clips. I think it would have been possible to remove the front panel without removing the warranty seal on the screws behind the speaker - just removing the middle screw is probably enough to get the front panel off.
I bought a USB socket from RS Components and it soldered easily onto the circuit board, then just had to cut the back panel blank out and it went together nicely. Now if you plug a USB memory stick into it, an extra menu item appears on the Freecom Nashville application menu, and you can play music off it. I haven't tried to disable writing to the memory stick as they did here because I think I will want to write to it from the musicpal. We'll see....
Haven't tried running software off it yet though.