OK, I've cleaned up the Scheme48 back end a bit and put it up on the web; it's browsable in
http://www.bloodandcoffee.net/campbell/slime48/
and there's a tarball slime48.tar.gz in the parent directory. All of the code is in the public domain. (Yes, there are a lot of features yet to be implemented, such as, most notably, name completion and the inspector. I'll be working on them this weekend.)