There's nothing wrong with quitting a Ph.D. program. To me, it looks like you're bright and intellectually curious, but you've got enough sense to ignore sunk costs, which is a valuable skill to have in a startup.

Some places might ask for grad school grades - Google, I'm guessing, they're strange about that sort of thing - but in my experience this is pretty damn rare, especially when the grades are of questionable relevancy. Never happened to me. If it did, I'd just laugh. My grade in Old Church Slavonic simply isn't relevant.

I quit a Ph.D. in History and got my consolation MA when I left. In my experience, most people don't think 'oh, he dropped out of a Ph.D. program' (although I've never hid that), they think 'wow, he got a MA from Stanford!' Not taking the MA would've been silly - now, with some work experience, it doesn't matter, but when starting out it was really valuable.