This is simple interpret of R5RS Scheme language mostly written in C. Many parts of it were written in Scheme and can be completely redefined in runtime (parser, macroexpander, ...). It is fully working, not much slow and (perhaps) stable, but I don't see any reason to use it instead of the others (GUILE, MIT-Scheme, ...). Maybe as example to study - it is pretty simple.
Detailed documentation in english language included. You need Guile (with minor hack any other Scheme interpret) to compile this program.