"Sublime Text is better compared to Notepad++, Notepad 2, Gedit, SciTE, Emacs, and Vim, which are all open source software and extremely popular."
Fair enough. I use ST2 like Coda/Espresso/Brackets for my own front-end development b/c of the app's agility and abundance of useful plugins for the front-end.
Keeping Atom partially closed source, again pointing to historical marketability, could give it more credence among developers of both ends. There's a reason closed source, proprietary editors are so massively popular vs. open source editors which often can't seem to get meaningful market share (whether Enterprise or Sole Proprietor/Freelancer).
That said, I really wish an open source editor, on the front-end specifically, like Brackets or even Notepad++ would become something I want to use more than ST2, Coda, etc. but there's always something missing.
Atom has potential as a partially open source editor but it remains to be seen. I'll need to be drooling in order to truly make a switch.