Brainfish is a standard Stockfish chess engine extended by a general book format, which is capable of handling a reduced part of Cerebellum, which is an innovative chess opening and playing book. In BrainFish the Book moves are only used in engine games, not in analysis mode.
All moves in the distributed book Cerebellum_light.bin generated by Cerebellum where calculated by using Stockfish as analysis engine, without using statistics. Then those moves where again recalulated by the Cerebellum Library using a graph algorithm which makes all scores in the library consistant. Consistant scores means for example when the starting position has a score of 0.2 and a best move is 1.e4, the position after 1.e4 must have the score -0.2. Additional some others properties are found like the best main line for a position and possible Transitions.
That means when Brainfish is playing, it plays like Stockfish regarding the evaluation, only a much higher skill level. The lines in Cerebellum_light.bin are in some cases reaching the late middlegame and endgame. Pondering is only active after the last move out of the book has been played
BrainFish is licensed unter the GPL, which includes the access code to the general book format.
Official Page and details: http://zipproth.com/index.html#Brainfish_download