Indeed, the SO codebase itself is not open. And with good reason; there are already a thousand garbage UI clones of the site. It's clear that if the code was a

Indeed, the SO codebase itself is not open. And with good reason; there are already a thousand garbage UI clones of the site. It's clear that if the code was actually open that there would be a thousand garbage clones chock-full of terrible ads, but the UI would be so good people would actually use them. That would dilute the quality of SO itself, and render it all less significant.