With utter love to ST and full respect to the author, I don't see how it's going to standup against Atom. There is almost nothing in Atom, that scared me off anymore. A lot of plugins and speed is absolutely great. Few lags but all of them upon first load. It's acceptable.
I must say, that I paid for ST licence and if I didn't I would probably love alternative even more.
In my humble opinion, in case ST doesn't go open source now, it won't matter at all in few years. With KickStarter author could rase lot of money. For example, FontAwesome already raised almost $1ml, just in about a month.
Imagine, that you could install ST and its plugins from CLI in Linux default distros? I don't know what's the revenue author expects but I think that it would be many times more with donations and KickStarter.
Otherwise, I will choose Atom just because it's, first, open-source, and second, because it works the same well (nowadays already)