>   The source code and the comments which are  
> not in English puzzled me a lot. 

Hum, yes, I know. But the worst part is that even if you 
understand french, you won't probably understand comments. 
The code is really badly commented, and many parts are also 
really dirty. I wish I have some time to rewrite the core 
engine (C++ ?) entirly :)

> Are there any documents 
> about development and introducing the architecture of 
> source code available?
No - this part is also missing (the design was described 
many years ago, but very briefly, and the description is 
not very helpful yet)