I've got µL up to a point, where I can start the REPL, load the compiler with a C-code backend, and type (make-system) to rebuild the whole thing as C-code. The way it works, I have a basic runtime library (ulisp.lib) with just the primitives, garbage collector and other essentials. Then you build an application with µL code "compiled" into C-code (chunks; you could load those dynamically too) that runs the code, without requiring the reader or the compiler. It's still somewhat more like "loading" though, in the sense that it essentially calls what the compiler would have called had it compiled things "on-the-fly."
So last time I was talking about C++, but I actually gave up on C++ on this project. Somehow I couldn't get the library API clean without making it all "C-like" and I figured I could just rewrite it as C. So I did that; it's all now plain ANSI C (for practical purposes at least). Rewriting it all took a day and ended up many times cleaner. Adding new C procedures (whether simple primitive functions or C-closures) is now very straight-forward and simple.
I guess it's starting to get to the point where it might make sense to put it online somewhere and attach an open-source license... if I can figure out what that license should look like.