Shoddy Battle - Pokémon Lab (formerly Shoddy Battle) is a free and open source Pokémon simulator created by Cathy J. Fitzpatrick and Benjamin Gwin.
Pokemon Showdown - Pokemon Showdown is a 2D, Fighting, Single and Multiplayer video game.
Tuxemon - Completely open source monster fighting RPG - capture and battle monsters against others!
Temtem - Temtem is a Massively Multiplayer Online and Role-playing video game released by Humble Bundle for PC and expecting to release for Console in earlier 2021.
OpMon - An open source Pokemon clone, with monster fights
Broken Ranks - Broken Ranks is a tactical turn-based medieval-fantasy MMORPG.