A "dialect" of MacLisp, the page says. I doubt there was any code in common.
The LOOP macro may have been derived from MacLisp.
If we ask what was Spice Lisp based on, I don't know if it used sources from a prior Lisp. Though there was an earlier C-MU Lisp, which was based on UCI Lisp, Stanford LISP 1.6,... Generally Spice Lisp was in the Maclisp camp.