I've talked to Chris Heald about this in the past. Like him and John Nunemaker, I'm no longer using MongoMapper on a day to day to basis (although I still use it occasionally for side projects).
I think the best way forward with MongoMapper is to open up contributions to anyone who has gotten a patch submitted (an "open commit policy"), as per Rubinius.
If you're interested in working on MongoMapper, have gotten a patch accepted previously and would like to work more on it, shoot me an email at sc...@railnewbie.com
. Put "MongoMapper" in the subject line, along your commit sha1, and your github username in the email. I'll add you to the project and you can commit away.
I know this might be a bit unorthodox for an ORM but I really believe in the contributions of each of the members of the open source community.
Hopefully this leads to a new flourishing of activity for a great project like MongoMapper.