Hey is a free download, but it's a revenue stream for Hey. And since it's free on the App Store, Apple makes nothing, and Hey reaps the benefits. That's dumb.
How is this dumb? For example, Lufthansa's app is free on the App Store, Apple makes nothing and Lufthansa reaps the benefits (otherwise Lufthansa would never bother to make the app). Why not force Lufthansa to pay Apple a portion of the plane ticket every time you check in with their app? The same goes for almost any other free app, most companies develop apps like Lufhansa's because they want to make more money, not less.