It might not be the smartest way of giving a zero-weeks notice at work, but you've gotta give this guy some credit for doing extra work and making a custom Mac OS X app just for the purpose of quitting.
Apparently the pop up prompt was seen by the fellow's coworker who explained the situation:
He believed he was in a temp-to-hire position, and after three months of extra hours and butt-kissing, turns out it's just a temp position. He was a good worker too. I'd have recommended him. Too bad he burned his bridges... Obviously he had contemplated quitting long enough to make this thing, but still refused to speak to anyone about his feelings. Ironically, he complained about the 'divas' at his last job.
Well, who'd want to keep him if he makes an app with prompts that don't even have functional buttons? If nothing, one of the buttons should've opened an email app with a pre-written apology note. [Method Shop via Cult of Mac]