One big mistake SourceForge made was not scoping repositories. There could only be one project of a name on the entire site, which is why there was manual review. People naturally wanted to participate at the one true project, not a differently named fork. This introduced the usual social issues of being the "official" project, who had and controlled commit access, etc.

Github smartly made it user/project so the same project name can exist any number of times, and it is only the top level user/organisation that needs to be reviewed.