I think I read Atlassian was going IPO this year which was why I couldn't dissociate GitHub from GrubHub for the longest time. Since they are both going after the coveted enterprise market, I automatically assumed it was GitHub and the IPO was to raise capital.
I'm wondering if these days "filing for IPO" is synonymous with "couldn't raise another large round." It seems so common for multi-billion dollar companies to do a huge private equity financing (+$100MM) to push off Sarbanes-Oxley a few more extra years.
Twitter, Dropbox, Facebook, Uber, GitHub, Airbnb, and Square have all done this. Maybe Goldman Sachs wasn't hungry for this one?
That reminds me http://en.wikipedia.org/wiki/Typoglycemia