What are some alternatives?
PokeMMO - PokeMMO is an Amazing, Action-Adventure, Massively Multiplayer Online, Role-playing and Puzzle video game that provides with the same mechanics and gameplay as Pokemon.
Pokemon Showdown - Pokemon Showdown is a 2D, Fighting, Single and Multiplayer video game.
EvoCreo - Embark on a journey through the world of Zenith.
Monster Park - Lovable monsters are out there! Walk into the meadow and catch 'em all!
Pokemon World Online - Pokemon World Online - Free Pokemon MMORPG.
OpMon - An open source Pokemon clone, with monster fights