Joker
This software is not developed anymore
Joker is a chess engine written at the end of '90s to study AI techniques for game programming (probably it contains one of the first implementation of the MTD-f search algorithm).
It's offered without support, as "historical" artifact, under the terms of the MIT license.
Further details at http://www.eosdev.it/joker/
If you like computer chess take a look at http://computer-chess.org and https://chessprogramming.wikispaces.com, you'll love them!