[dchuk]

I'm not well versed in the nuances of software licensing. Are there prominent examples of other projects using a similar setup? Or is Github unique in this?

Or is it a case where Github's size/reach makes them unique in this at scale?

[worldsayshi]

Correct me if I'm wrong but I think that some Microsoft products (.Net?) have a similar setup.

[chimeracoder]

We don't have any details of the Atom license yet, but it sounds like it will be equivalent roughly to Microsoft's shared source licenses for proprietary code: http://en.m.wikipedia.org/wiki/Shared_source