> GitHub has taken off like a rocket

I think this is in part because they charge. I like this model. Its simple. You want to use GitHub for free then you have to make your code freely available. You want to keep it proprietary then you have to pay for your account.

Where this doesn't translate well with SourceForge is that it was designed from the start to be of, by, and for Open Source projects. So the vast majority of projects would be non-paying.

However, they may be able to add some features that appeal to proprietary projects who are willing to pay and use that revenue to offset any losses. It would be hard work but ultimately I think it would be be better than the appearance (if indeed it is just that) of distributing malware.