Your request would already be fulfilled if PulseAudio wasn't so horribly broken. The package pulseaudio-module-extra contains module-native-protocol-tcp.so, but trying to load it fails.

On the desktop, I am using Kubuntu 9.10. I also tried running paprefs and checking "Make local sound devices available as DLNA...". This should be visible in the N900 media player, but it seems to fail silently and doesn't even open a new port on my desktop.

PulseAudio could be great, but so far all it's accomplished is screwing up my sound every time I upgrade.