Incoming links: Chess UI
The user friendly Chess UI! Exactly what you would expect from a GNOME Project package. But also packs some punch via the Universal Chess Interface, e.g. Stockfish just works.
Both chess engine and a CLI chess UI. As an engine it is likely irrelevant compared to Stockfish as of 2020. TODO: does the UI support Universal Chess Interface?
Cool project history though. Started before the GNU Project itself, and became one of the first packages.