Steel Bank Common Lisp (SBCL) is free software, and comes with
absolutely no warranty.

SBCL is derived from CMU CL, which was released into the public
domain, subject only to the BSD-style "free, but credit must be given
and copyright notices must be retained" licenses in the LOOP macro
(from MIT and Symbolics) and in the PCL implementation of CLOS (from
Xerox).

After CMU CL was released into the public domain, it was maintained by
volunteers, who continued the tradition of releasing their work into
the public domain.

All changes to SBCL since the fork from CMU CL have been released into
the public domain in jurisdictions where this is possible, or under
the FreeBSD licence where not.

Thus, there are no known obstacles to copying, using, and modifying
SBCL freely, as long as copyright notices of MIT, Symbolics, Xerox and
Gerd Moellmann are retained.