Sourceforge? Ohloh collects stats and information from all over, they even have a Mongrel2 project page and I've never set it up. I'm pretty sure you're mistaken about the kind and quality of data they collect, but who knows. Their blog seems to say they track git, cvs, svn, others?
That's also why I mentioned github, they could provide other data (if they weren't too busy inflating their numbers by counting every commit, gists, forks, and duplicate projects as a "project").
They can track almost anything, but require somebody to manually create the project and "enlist" it's source repositories. And because often the person who created the Ohloh project has almost nothing to do with original project these data tend to get stale.
My theory: projects migrate away from sourceforge and don't bother to enlist new repositories in ohloh.