I dont know where to get it exactly, but the way it works is its basically a user based fighting game. Users can create their own characters using existing sprites (or creating their own, if theyre really good), and program movesets, etc to them. So its pretty cool, my neighbor has like all the Street Fighter characters, some Marvel characters, and some random stuff like Metal Slug characters and even the duck from Duck Hunt! Basically, its easier to get sprites that already exist into the game, as all the moves and sprite animations have to be hard coded I believe.
Anyway...just try searching Google to pick it up, thats my suggestion. Its pretty cool if you can find some user-posted characters to download.