GNU CLISP is an UNIX/Windows implementation of ANSI Common Lisp with many extensions.
GNU CLISP is a Common Lisp implementation. It implements the language described in the ANSI Common Lisp standard with many extensions, and runs on most UNIXes and on Microsoft Windows. It has an interpreter, a compiler, a debugger, and implements most features expected of a modern Common Lisp, including CLOS, MOP, an FFI, Perl and Posix regexes, and others.
GNU CLISP is distributed under the GNU GPL, but its copyright file specifies that it can be used to compile proprietary applications.