Check DLNA specs. Or go to http://live.gnome.org/Rygel and check there, this is the implementation used on the Harmattan platform. Practically, all UI would need to do is to set appropriate bit in Tracker database and have rygel service started.
I cannot dive into details why and how Nokia does its own product development. If you need some verification, you may check my profile on maemo.org (same nickname as on TMO).
These threads, unfortunately, full of analysis of technical details done by people with little or not engineering background, thus many factual errors are present.
If a mere attempt to correct those meets opposition, so be it -- I'm fine not to fight insisting dark ages knowledge.