Mysterious New Badge

[Marmot]

There are quite a few Mega Milestones that are unexplained and you only tend to find out about them when you hit them! And even then it's not always obvious why you got them!

I had no idea what the MM badge itself was, that it comes from Free-DC instead of a project, that it means MegaMilestone, why it showed up nor why it's bronze instead of silver or blue. The FAQ isn't helpful and a forum search returns:

The following errors occurred with your search
The following words are either very common, too long, or too short and were not included in your search:
MM

So now after an 90 minutes of searching around at least I know it's MegaMilestone and it's from FreeDC but still not sure what triggered it and how to get the next color badge.