At the beginning, maybe you sign up some super high-end 10X developers to do reviews. Also run some tools like SpotBugs or Coverity or something.
Then when the ammount of reviews goes up by 10X, what are you going to do? You can't possibly find many 10X developers that are willing to review random crap code.
So you end up reselling cloud-based Coverity licenses (SpotBugs is free).
Also, this only works if the company is willing to share its code with a random startup. Which is kind of a no-go for large shops. So who do you sell to? Large shops won't allow access to their code. Startups would, but they either won't pay in principle (hey we can use SpotBugs or Coverity) or won't pay much.
Can you make a business of it? I don't know, but there are some investments being made, so I guess there is a better story than the one I see.