A few days ago I released a new version of Fairy-Max, which fixes a few bugs and imperfections that showed up in version 5.0a that was released last month. See:
Version 5.0a involved major refactoring of the code, to make Fairy-Max capable of handling boards with other than 8 ranks. This allowed adding the variants Los Alamos Chess, Roman Chess, Mexian Chess, Ciccolini's Chess, Wildebeest Chess (well, nearly) and Grande Acedrex. Of course the variants on 8-rank boards (normal Chess, Shatranj, Makruk/ASEAN/Ouk/Ai-Wok, Courier Chess, Knightmate, Berolina Chess, Capablanca/Gothic Chess, Chess with Different Armies (FIDE/Clobberers/Nutters/Rookies), Team-Mate Chess and Bifurcator Chess).
Compared to earlier versions Fairy-Max 5 also supports analysis mode, and a persistent hash table that can be used to construct opening or end-game books, and can recognize repetitions of positions in the search (allowing it to plan sacrificial perpetuals).