What initially seemed like a somewhat clear question has caused a lot of research looking at specific language of several rules, which in and of itself is a good thing. That research causes me to reverse my position on this question.
Considering that the snapper was in possession of the ball, and that when he began the snap (NF: 2-40-2) the ball became alive, and that a "runner" having a knee on the ground while possessing a live ball, renders the ball dead, (NF: 4-2-2-a)and that any player in possession of a live ball is a "Runner" (NF: 2-32-13) seemed to point towards the ball being dead once the snap began with a knee on the ground.
However, "Upon further review" and consideration of NF: 2-34-1, which states, "A ball in player possession is a live ball held or controlled by a player after it has been handed or snapped to him or after he has caught or recoverd it, it seems my previous conclusion falls apart as the snapper's grasping the ball to snap it, having NOT been handed, snapped, caught or recovered by the snapper doesn't meet the requirements of possessing a live ball, which means he's NOT in "player possession" of the ball, which means he's NOT a "runner", which means NF: 4-2-2-a, "the ball becomes dead when a runner.....allows any part of his person other than hand or foot to touch the ground.", doesn't apply to this situation.
Once again, it seems, the more you think you know about Rule 2, only underscores how much you have yet to learn.