You can find Rybka 4 bundled with the Aquarium GUI at ChessOK, which offers advanced analysis tools like Interactive Deep Analysis (IDeA).
If you're looking to , this guide covers where to find it, how it differs from previous versions, and what you need to run it. Where to Download Rybka 4 download rybka 4 chess engine
You can purchase the plain UCI version (without a Graphical User Interface or GUI) directly from RybkaChess.com . You can find Rybka 4 bundled with the