Emacs
is not just an editor. Some say it is an operating system. And yes, it
comes with its own language: Elisp. There
are lots of applications for Emacs under Elisp. One of the most
impressive and that shows much of the power of elisp is Calc, a computer
algebra system running under Emacs.
Prolog
SWI-Prolog, a good Prolog implementation under the GPL
See also the resources
for my AI lectures
Last changed at Wed Feb 15 15:05:35 2012 by D. Polani