Firmware
Near as I can tell the rocbox uses the PortalPlayer PP5020 chipset, it's like an "all-in-one" chip. The iPods use this chip too. I've tried to decode the database for this thing so we can all stop using WMP and move to a much better winamp plugin or similar, but no luck. I have also tried to get into the firmware, there are many features that I would like to improve. I have emailed support to find out if the firmware is open source, so we can start improving on it. I'll post a comment when they email me back.