I think that the Macsyma company used Austin-Kyoto-Common-Lisp
(which I believe is related to GCL) for its unix-sun/hp/.... version.
GCL is the same program as was formerly called AKCL. The developers
agreed to make it a GNU package.
I believe Macsyma is released under the GPL now, so there would
be no difficulty running it on GCL even if GCL were GPL'd.