Apple has responded to the furor over its supposed App Store policy changes that many believe could affect the popular Kindle, Nook, and Sony Reader apps. The company claims it has not changed any of its guidelines given to developers, but it indirectly confirms that accessing content purchased elsewhere could be a no-no if that content isn't also available to be purchased through Apple's own system.

"We have not changed our developer terms or guidelines," Apple spokesperson Trudy Muller told Ars. "We are now requiring that if an app offers customers the ability to purchase books outside of the app, that the same option is also available to customers from within the app with in-app purchase."

Buzz began Tuesday morning when the New York Times said that Sony's e-reader app had been rejected, citing Apple's restriction on in-app book purchases. This in itself was not a new policy—Apple doesn't allow apps to sell content to users unless that content passes through the official Apple ecosystem, where Apple gets a 30 percent cut.

Apple also allegedly told Sony that the app couldn't access content purchased on other Sony Reader devices, which is where most of the outrage was focused. Amazon's Kindle app and Barnes & Noble's Nook app are both popular mechanisms for users to download and read books that they have purchased from the respective stores. Many feared that this supposed change in Apple policy would take their e-books away from their iPads, iPhones, and iPod touches.

Apple's second statement indicates that this is indeed the case—sort of. If an app lets users access content that they purchased via Amazon's website, for example, then that same app must also let users buy the same book via Apple's own in-app purchase system. If the app developer doesn't want to use Apple's in-app purchases to sell content, then the app can't access content purchased elsewhere either.

This is notable because it will require Amazon and Barnes & Noble (as well as Sony, whose iOS app is not yet available) to change how their offerings work. Apple wants its 30 percent share of content sales whenever possible.

Amazon has already gone all-in with its "Buy Once, Read Everywhere" tagline, so it probably can't afford to back out of the iOS platform now. The alternative appears to be an user interface nightmare: re-structuring its sales mechanisms in order to allow customers to buy from both Amazon and Apple (a move that will chafe Amazon execs) or from Apple alone (even more chafing).

Sony, for its part, still has not responded to our requests for comment. The company did post a note on its website, however, noting that it has "opened a dialog with Apple to see if we can come up with an equitable resolution but reached an impasse at this time." The company says it's exploring other ways to bring its Reader to iOS devices, indicating that it may try other routes in order to avoid the App Store tax.