Linuxlookup did a comprehensive review (from a hacker's perspective) of the OSD.  The firmware might have been slightly out of date, since the multimedia performance seems like it had issues that we have already solved, but if you're a hacker looking to get into the OSD, this is a good snapshot.  Xorlev and others are working on improving the build system with scratchbox, but as always, your help is welcomed!