The Kindle app—and other e-book apps like it—may disappear from the App Store if the latest buzz about Apple's policies turns out to be true. According to a report in the New York Times, Apple has rejected Sony's e-reader app because of a policy change at Apple. Under the new policy, apps can no longer access content purchased outside the App Store.

It appears as if Sony's app tried to offer a built-in bookstore as well as the ability to download books purchased on other devices, but that idea was shot down when Apple reportedly told Sony that all in-app purchases must go through Apple. This is a controversial—but not necessarily new—policy, and the same reason why Amazon's Kindle app doesn't have a built-in Kindle store. Apple also supposedly said that apps like Sony's can't download content that users purchased elsewhere.

If that's an accurate description of what Sony was told, then it's possible that Amazon's popular Kindle app may soon be in the crosshairs as well. Users have long been able to use the Kindle app to access the e-books they purchased on a computer or a actual Kindle device to read, make notes on, and sync across other devices; it's arguably one of the main iBooks alternatives that e-book aficionados use on Apple's devices.

Unsurprisingly, Sony isn't happy with the decision. "It’s the opposite of what we wanted to bring to the market," Sony spokesperson Steve Haber told the Times. "We always wanted to bring the content to as many devices as possible, not one device to one store."

That's certainly what Amazon wanted to do as well—one of the company's main taglines is "Buy Once, Read Everywhere," and Amazon brags about the success of its iPad and iPhone apps. If the report ends up being true and Amazon's app falls victim to a change in Apple's policies, we're sure to hear a wave of complaints from angry customers from both the Apple and Amazon sides.

None of the companies—Apple, Amazon, or Sony—responded to our request for comment before publication time, but we will update the post if we hear back. (Update: Sony has added a note to its website about the supposed policy change, but there are no new details about what, exactly, Apple told Sony.)

(Update x2: Apple has responded to the furor, confirming to Ars that parts of the speculation are indeed true.)