Does anyone here know if it's possible to 'fake' an AirTunes interface on a PC?

Basically, what I'd like to do is use iTunes on one PC to stream music to another PC on my LAN that's hooked up to my stereo, while allowing me to control the playback on the main PC. iTunes already has an interface built-in to do this, but of course it's limited to their proprietary AirTunes box. I don't want to buy yet another box and TBH I don't have a free input for one on my amp either. ATM I use the Rendevous sharing system in iTunes and VNC to the remote machine, but I wonder if there's a better solution.

I did some searching and found a few bits of reverse-engineering have been done on the ALAC codec and RAOP protocol that Apple uses. But does anyone know if any of this has been put together into an actual interface?