Assuming the founder is unaware of the situation (if he is, I would advice you to find another company), then he probably cares more that anyone else about the business succeeding. From that perspective, he will be very attentive to what you have to say, and thankful for you bringing it up.

Now there are a few different ways to break the ice. I would start with something positive as most people don't like starting a discussion with conflicts. Maybe tell him about how you're excited about your work, because seeing clients happy and satisfied gives a sense of purpose and achievement, while strengthening the company brand. At the same time, you've noticed (and it pains you) that other projects are not being delivered, and causing clients to be lost, and the company looking bad. Share some evidence (a.k.a facts) that brought you to this conclusion, and if possible a way for his to double check. From there I'd play it by ear depending how the conversation is going. One thing to keep in mind however, is to see whether he knows already or not... if he does approve of such practices, then it's probably not a place you want to work at. Good luck :)