[skywhopper]

I think calling it "hackable" is a little bit of a fudge on Github's part, but from what I can see of Atom, it's open enough that I'm okay with their characterization. Certainly it's more open and hackable than github.com itself.

[maxerickson]

I would go in the other direction and say that 'hackable' is so fuzzy that it doesn't mean anything.

"I hacked this wood and made a spoon."

"I hacked my breakfast."

I do get that there was at some time a group of people where it had a clearer meaning.