[philipkglass]

I would say no to the second PhD. If you're motivated enough to get one PhD and to start your own company you're motivated enough to do some research on the side (if necessary) while working in a software job. You'll be a lot better able to save up money for your future company if you are working in an industry job, and in industry you'll acquire kinds of experience that are hard to get from any PhD program. Finish your current PhD, get an industry position, and once you're settled in start doing your own side self-education and research. (Assuming that your day job doesn't naturally afford you opportunities to further sharpen your interest in and knowledge of specific AI areas.)

Research publications aren't important if you want to start your own company. You're not trying to impress yourself enough to get hired by yourself. But doing research-y things, like finding a recent research result that interests you, reproducing it, and trying to improve upon it, still might be important. Even better, IMO, may be looking at recent research results from groups that share source code, and testing your skills at turning research-quality source code into industrial-quality code. That might have to wait until you've been in industry a few years and have a better feeling for how robust production-quality code differs from research code.