As of now, the only commission free booking engine I know of is buuteeq’s, which doesn’t interface and provides a nightmare for inventory management. The only interfaced to PMS, commission free booking engine that I have ever heard of or known is Mirage Hotel Systems, who built their own that they offer with their PMS, which is also my favorite. I wouldn’t hesitate to buy it, in a heart beat. It’s astonishing more PMS don’t do this to secure more clientele.