They could start with a specific list of allowed uses: * purchasing a physical item * purchasing an electronic item accessible outside of the app * subscribing

They could start with a specific list of allowed uses: * purchasing a physical item * purchasing an electronic item accessible outside of the app * subscribing to a service accessible outside of the app * purchasing things through the app owner's own payment gateway And then expand from there as necessary. Probably the restrictions would need to be tighter than that, but something along those lines.