there is a doc on the game engine at
www.goutai.com/blender/architecture.zip

also I saw a circular dependency that creeped into the game engine two days before the release (bad!)
I will remove it (expressions lib and game logic lib should not be dependent on ketsji, so the include is wrong). KX_Python.h and two other files are in the wrong location, should be in expressions.

Hi, Erwin!

This documentation is so interesting thing, and helpful for gameengine developers...
Thank you for sharing!

and, Do you think about the ODE?