Any Wii or Wii U user can easily install and play the mod without any hardware or software modifications.
Project M is an ambitious mod for the Wii's Super Smash Bros. Brawl, aimed at bringing Brawl up to the same competitive standard as the GameCube's Super Smash Bros. Melee, while adding some new characters, stages, and features along the way. Version 3.0 of the mod has just been released, and best of all, it can be installed onto any Wii or Wii U without having to perform any kind of hardware or software modifications.
Version 3.0, as well as adding Samus, Kirby, Yoshi, Ice-Climbers and Olimar (thus completing the entire Brawl roster) actually adds two completely new characters that were playable in Melee but absent in Brawl: Roy and Mewtwo. As well as this, many existing characters have received new alternate costumes and models.
The latest version of the mod also features the addition of "turbo mode", a game type in Special VS which allows any character to interrupt moves once they've connected with an opponent. "Chain attacks together to create Turbo speed combos limited only by your imagination and dexterity."
When Super Smash Bros. Brawl was released, the fanbase of people who like getting a bunch of mates together to beat the snot out of Nintendo mascots were thrilled. New characters, new stages, new features! The hardcore fanbase who played the game at a tournament level, were less impressed, lamenting the removal of features such as wave-dashing and the addition of curiosities such as tripping.
As such, Melee has still remained the tournament standard, being played to this day at major tournaments such as EVO. Project M aims to change all of that.
Source: Project M