The obvious answer is to end free unlimited private repos. Source is no longer a specific thing. GitHub is just a free S3 or Azure provider.
You can also limit number of free commits to, say 100 per month.
Public or private doesn't matter. Vibe coders aren't worried about others using their AI slop
I think this would cut out a lot of the mindless commit activity.
Charge $1/month per repo. If your project isn't worth that, run your own git or use another free forge.
I would have thought it's public repos that got the most AI slop recently as a form of gathering karma and boost CVs. It would be nice to know if private repo commits increased instead.
A lot of private repos are probably just taking up cheap storage space, not seeing activity that would cause additional load.