Christian Pinders "Elite: The New Kind" is worth a mention. It was released around 2002 I think, and unfortunately relatively quickly withdrawn due to a request from Braben, I believe.

The New Kind was a re-implementation of Elite in C that largely tried to follow the way the original worked, while remaining readable C.

I hacked on my copy for a while to port it to OpenGL, add some particle systems for explosions, and embed ppmforge (I think, it may have been another fractal planet generation tool) to create fractal planet surfaces (just a quick hack to add a texture on a sphere that looked nice from the air, I didn't even begin to think about adding code to land etc.)

Pinders original source shouldn't be impossible to find. It's worth a look.