<DouweM> kevinsawicki: is the actual core going to be OS?
<kevinsawicki> DouweM: not during the beta
<tyOverby> How is atom both invite-only and open source at the same time?
<avidal> tyOverby: the engine isn't open source (or at least yet)
EDIT: Plus, if an editor is going to join the ranks of vim and emacs in history (something which neither Sublime nor TextMate are on track to do) it has to be open source. Anything else and it's just another product.
Tools work in a strange way. I recently saw a whole team of embedded developers use TextPad. They haven't heard of anything called 'vim' or 'emacs'. From their perspective its either a vendor supplied IDE or TextPad. One of them was even startled to see this shiny new thing called 'Sublime Text' when I was using it. He went out with enthusiasm, but was hardly able to convince any one to use it.
A code editor with first class prominent Github support is more likely to encourage creating Github accounts - it would just work. Compare to regular code editors which require jumping through various hoops (typically having to find relevant plugins, install them on all machines/users, and then figure out how to use them as they are extensions not core).
A pitch of "if you use this editor then all the team's work is automatically synchronized and available" is a very powerful sell.
Not for me. I do like to give new editors a try (fell deeply in love with LightTable just a short while ago), but OS X as main platform and yet another closed editor?