Apple deliberately hinders Progressive Web Applications on iOS Safari, effectively stifling innovation. Look at how many requests are there on WebKit to implement many of the features/API's required.
They don't even allow competing browser engines. Chrome, Firefox etc on iOS are just wrappers around Safari.
This is where I think they might be legally vulnerable, if anywhere. Especially since Jobs initially answers the shocked reaction of 30% by "it's no big deal everybody is going to make web apps anyway."
They don't even allow competing browser engines. Chrome, Firefox etc on iOS are just wrappers around Safari.