Yeah, IMO, sourceforge and github never competed. Sourceforge was a place to host installers for windows shareware. Github basically created its own market. It was really competing with the millions of private SVN servers. When git became the new hotness, anyone who researched it realized they could just use github instead of having to stand up their own git server. It was a zero cost trial of git, and basically everyone chose git over svn and just stuck with github.