I don\'t know exactly how it works either, but my guess is that they are x86 binaries with known entry points in the DLL, so the linux code just finds the entry points and calls them. At any rate, mplayer for Linux WILL load and use win32 binary codecs which allows it to play most rm content.
There is supposed to be a helix port to arm to support the new motorolla smart phone that is Linux-based, but I have not seen any activity over there. That will be the best bet for NATIVE playback.
In the meantime, using my linux box and mencoder works best for getting RealMedia or WMV streams in a format that can be played on my z in near-real-time. I use it for live baseball and as long as I give it about a 20 minute delay it plays flawlessly.
ThirtyOne