History of Math.SE in general is recorded at http://meta.math.stackexchange.com/q/7021/79365
The users most active in private beta phase, when the site was just getting started, are listed here.
As his profile says, Dan Dumitru is a programmer. His vision for the site can be inferred from the three questions he contributed to the proposal when it was in the definition phase.
Given the coordinates of a triangle's corners, what conditions guarantee that the point P(x, y) is inside the triangle?
Dan's comment: "This is a math question a software developer might have"
How can I calculate the shortest distance between 2 cities, having their latitude & longitude?
Dan's comment: "this is a real world question, and it goes without saying that it's the arc along the surface, and not digging a tunnel through Earth to get from one city to the other."
Can someone solve [2x^2 + 3x + 2 = 0] for me? [closed]
Dan's comment: "Blatant homework questions should be off-topic, if the OP doesn't prove that he has put at least some effort in solving it and coming up with the right question to ask."