Also, this conspiracy requires coordination across two separate companies (GitHub for the repos and the LLM providers requesting private repos to integrate into training data). It would involve thousands or tens of thousands of engineers to execute. All of them would have to keep the conspiracy quiet.
It would also permanently taint their frontier models, opening them up to millions of lawsuits (across all GitHub users) and making them untouchable in the future, guaranteeing their demise as soon a single person involved decided to leak the fact that it was happening.
I know some people will never trust any corporation for anything and assume the worst, but this is the type of conspiracy that requires a lot of people from multiple companies to implement and keep quiet. It also has very low payoff for company-destroying levels of risk.
So if you don’t trust any companies (or you make decisions based on vague HN anecdotes claiming conspiracy theories) then I guess the only acceptable provider is to self-host on your own hardware.