We use both. SourceForge brings to the table a huge distribution network. Webmin burns terabytes of transfer for millions of downloads every year. I'm not sure github is even in the game on that front, are they? They also host the webmin.com domain, for the time being, which saves us some bandwidth, as well.

But, we never used the VCS at SourceForge, and we barely touch the forums and bug tracker...if we could turn them off, we would.