Okay, for everyone who doesn't know what this is about, here's a short info part for you explaining it :
SDL stands for Simple Direct Media Library (get more infos
here ) rather than the DirectX libraries. Consequently, it can be used on many different platforms, while still using the excellent core from the windows version.
What does this mean ? This means that, once SDL is being used, the emulator will run on many different platforms, like linux, BeOS and, of course, still windows.