I agree that the current members of our organization on GitHub are probably the best starting point.
Those people should then be visible
Very good point, as we want to make these decisions more transparent, it’s only logical that information about who makes the decisions is public.
How do people get to be Commiters? Do the other Commiters vote on new people?
That would be the (at least mine) idea. To quote the “Producing OSS” book:
The voting system itself should be used to choose new voters, both full and partial. But here is one of the rare instances where secrecy is appropriate. You can’t have votes about potential new maintainers posted to a public mailing list, because the candidate’s feelings (and reputation) could be hurt. Instead, the usual way is that an existing maintainer posts to a private mailing list consisting only of the other maintainers, proposing that someone be invited to join. The other maintainers speak their minds freely, knowing the discussion is private. Often there will be no disagreement, and therefore no vote necessary. After waiting a few days to make sure every maintainer has had a chance to respond, the proposer mails the candidate and makes the offer. If there is disagreement, discussion ensues as for any other question, possibly resulting in a vote.