I think it's important to separate its positive effects on the community from the merits of its UI. To me, SourceForge epitomized the "it's complicated for us, so it should be complicated for you" school of UI design. The owners didn't appear to do much to improve that over time, instead treating the site much like toxic code that no one dares to modify for fear of breaking something. No doubt that was a huge factor in their decline, which fed into the user-hostile cash grab tactics. However, the fact that it existed at all when no alternatives were available was great. I wish the new owners the best of luck in turning the site around.