I guess we don't agree on what "tons" means. I don't remember searching through millions of projects on source forge.

So, the fact that people didn't stop producing new software when github was created is because github was created?

Or the fact that there are more software developers in the world today than there were when github was created wouldn't have happened without github?

Or is it that because sourceforge wasn't a quasi-monopoly, therefore everything that was not on sourceforge didn't exist?

Or what exactly is your point?

Sourceforge was definitely a "quasi-monopoly". If you weren't on Sourceforge you had a much harder time gaining credibility. There were also other projects that didn't use Sourceforge just like there are projects that don't use GitHub now.