It was just a small idea I had following some fun activities that I've done with friends, I saw the likes of Mega Man Infamous Intent at the time, and had the idea to give that a shot, maybe something cool would come out.
Formally, though, we did get started around December of that same year. That's when a few of us on the team made the push to get several artists, programmers, musicians involved with the project. (and while we got a lot of people interested, it was super early on - if you want to develop your fan game, I highly advise against making it public too soon, a mistake we've made.)
The game has gone through many different iterations since the project first started with multiple programmers. The game was originally going to use the "Mega Engine" framework but it's now almost completely custom made. Even some of the playable characters and original Robot Masters were changed during development. (R.I.P Spook/Fright Man. You lived as you were.. dead... Undead?)
We certainly had our lows, our highs, and everything in-between. I think it's important for people to recognize that making a fan game (or a game in general) isn't easy at all, even if you have a tonne of help from other people or whatever - we're all just doing this in our spare time.