@dorfd1: Anyone will be able to test this. Once I am done implementing and testing this a bit, I will push the changes to svn. You should be able to test it with an ext3 firmware, and use it like this until a new firmware is released.
Last night I finally managed to get XBMC to play a youtube-susbscriptions clip from this modified UMSP. It took me a couple of weeks of intense packet captures and analysis to get here, so I am close to success. Sadly, in the process I broke playback on the WDTV, but I will look into it and fix it.
I will need to do more testing - at least with an audio plugin before I can release the changes. I want to know that the UMSP code has the necessary changes to return compliant replies to other DLNA renderers.
Sadly, all the plugins will need to be changed slightly to work, but so far the changes are not that difficult to make...
I have a bit of time to experiment today and I hope I can get close to a final release. I hope some time next week the changes will make it to svn