Earlier quoted context omitted.
Necessary but not sufficient. There would be no free GitHub repos for open source without the income from the closed source repos that pay for them. As usual, open source is subsidized by closed source.
Maybe not "github" repos, but other public git repos would pop up. Suggesting that open source wouldn't have distribution is ignorant of the origins of open source.
GitHub isn't just 'distribution' it has required a huge amount of investment and focus by individuals who need to make money to feed their families and prosper.
The fact that it is GitHub that we're talking about, and the fictional repos that you imagine would spring up proves the point - in the real world, open source is subsidized by closed source.