Here is the original discussion  on the private list (over 2 years ago!).
I'm surprised these people have kept on with the project. While not as formal
as what some projects do (having a formal VOTE thread), it's up to each PPMC to
decide (and hopefully document) on how to appoint committers and it looks like
the consensus was to add the people discussed. I suggest you have a discussion
on the @private list and if there's no PPMC objections (seem unlikely) just go
ahead and add them as committers perhaps with an apology for taking so long.