The project definitely accepts contributions, the mbin devs have contributed to kbin before and a few weeks ago a minor code change was committed and merged by someone other than ernest.
As I understand it, the issue is that people with merge permissions other than ernest are only allowed to merge their own pull requests, not those of third parties, which require a review from ernest.
(At least that's what I've seen explained before, though I haven't seen any proof of it so I don't fully know if it's real.)
This means a majority of contributors can't get their pull requests merged when ernest is gone. Which is why they went and made mbin when he was gone for months last time.
NotTheOnlyGamer