CuckooChess is an advanced free and open-source chess engine under the GNU General Public License written in Java by Peter Österlund.
CuckooChess provides an own GUI, and optionally supports the Universal Chess Interface protocol for the use with external GUIs such as Arena.
The name CuckooChess comes due that the transposition table is based on Cuckoo hashing.
[2] Android app based chess gaming app Droidfish employs both CuckooChess and Stockfish chess engines.
[3] Similarly, Kickstarter funded AI based virtual reality chess game Square Off also uses CuckooChess engine.