He is welcome to open a channel with Babel privately and, if unaddressed, make a proper statement about it. Blasting someone by using GitHub contributions as KPI on Twitter is highly unprofessional and awful behaviour
It seems it has gone past that. If it is an accusation of theft (or what he perceives to be theft) he is surely allowed to say it publicly. You can still give them both the benefit of the doubt.
You must have never talked to someone who can't be reasoned with. It is best to do some of these things in public. The conception of libel that, say, the UK has is quaint and open to abuse. No such issue in the US.
I agree there's problems with looking at the proposed KPI but that does not mean it is pointless to speak up. For the vast majority of people you could ask about this, pulling that kind of money from a nonprofit is ridiculous.