Because the original developers ceased official distribution, you must now use community-maintained mirrors and spiritual successors:
Project M is widely regarded as one of the most successful fan-made video game modifications in history, transforming Super Smash Bros. Brawl into a fast-paced competitive title inspired by Super Smash Bros. Melee . Although official development ended in 2015, the community continues to maintain various versions and successors. Where to Find a Project M Download project m download