I do mean Common Lisp. I think that it'd be preferable for Guix to use it because Lisp is more production-ready than Scheme: it standardises things that Scheme — even R7R2 large — doesn't; it's a pragmatic production language into which a lot of experience went. And of course there's CLOS, which is absolutely awesome. Even better, a well-written Guix-Lisp would be portable between multiple Common Lisp implementations; it's extraordinarily difficult to write a real system in Scheme, precisely because Scheme is so under-specified: really, Guix isn't written in Scheme; it's written in Guile Scheme.

Scheme is neat, and pretty, and very elegant, but it's not (even in its largest, most recent version) really meant for serious use on large systems. And I don't agree that it's a Lisp: it has only a single namespace, it breaks (car nil) → nil and (if nil "true" "false") → "false".

I'm aware that rms dislikes Lisp and wants Scheme to be GNU's extension language; IMHO he's wrong, and his attitude has really held back GNU, Emacs and the Lisp world at large. Had it not been for that attitude, we might have a Common Lisp Emacs by now, we might have a Common Lisp GNU userland by now, we might have a GNU which really is Not Unix, instead of a mess of C, security bugs & hacks.