Its par for the course. You can't buy a Kobo book on a Kindle.
The question of course is an iPhone a specialized device or a general one. I would say Apple has worked as hard as it has to keep things locked down so it can say, with a straight face, that its platform is no different than a Kindle or a Leapfrog.
Its just a very successful specialized device that 3rd parties have decided to come and join the party (hosted by Apple.) So much like Xerox successfully fought off becoming a generic term, Apple is fighting off becoming a legally generic platform.
Compatibility isn't an issue either. The analogy fails: I've got Kindle books that have a back page directing me to the publisher's website to buy more.
Apple's rules would prohibit it.
Apple's restrictions on any content that suggests the consumer may access services by any means other than making an in-app purchase are not "par for the course", they are an unusual abuse of market power that directly misleads the consumer.
I've also just re-read the App Store rules and noticed that for multi-platform services, it even contains a covenant outside of the walled garden: "your general communications about other purchasing methods must not discourage use of in-app purchase."
The question of course is an iPhone a specialized device or a general one. I would say Apple has worked as hard as it has to keep things locked down so it can say, with a straight face, that its platform is no different than a Kindle or a Leapfrog.
Its just a very successful specialized device that 3rd parties have decided to come and join the party (hosted by Apple.) So much like Xerox successfully fought off becoming a generic term, Apple is fighting off becoming a legally generic platform.