God, seeing straight C programs that don't use any superfluous libraries or stupid coding tricks that just obscure the intent of the programmer is so refreshing. Just one C file that anyone with a barely working knowledge of C can understand and a very clear Lisp implementation.
Just don't try to learn C from it; code is saturated with boundless copying into stack buffers.
Not and IOCCC entry; just something Lispers carry with them when heading towards obscure and very small territories. You might like XCL better: http://armedbear.org/ has a native optimizing compiler and compiles to ~5MB for compiler + runtime.
I live in Australia now, mate. Sydney. It's like D.C. but with a beach, nicer beer, better public transport and laid back people :-)
Just don't try to learn C from it; code is saturated with boundless copying into stack buffers.