Mmm, but the question is, the data's probably going through some other port/protocol... at least for the mac version, there was a notice of "streaming" along with a percentage next to it. And there doesn't appear to be any of the loading-in-blocks that you occasionally see in the browser based version.

Still, I guess, once you save those packets, and reverse-engineer them, you could write your own client... I'm not too sure what linux has, in terms of a graphics rendering engine, but I'm pretty sure there's enough stuff there...

...maybe a combination of some open-source 3D gaming engine (Quake/Unreal tourny?) Imagine being able to fly around the world like that......