Apple's newly enforced policy banning links to out-of-app purchases has forced The Wall Street Journal, Amazon, Barnes & Noble, and Kobo to remove purchasing options from their iOS applications, while the Google Books application has been completely removed.

The Journal detailed its own situation, along with the effects on other App Store software, in a report filed on Monday. In it, the paper revealed it will no longer sell content directly to customers through App Store software, bypassing Apple's 30 percent cut of all in-app sales.

Previously, the Journal was circumventing Apple's in-app purchasing system by providing users a link to its website from within its iPad application. In February, Apple revised its iOS terms of service and banned such links, requiring all content purchases or subscriptions to go through its own system.

Apple softened its stance in June, when the company decided it would allow out-of-app purchases to have lower prices than those made available with in-app purchasing. Previously, the company had required that subscriptions sold outside of the App Store umbrella, where the company does not receive a 30 percent cut, to be "at the same price or less than is offered outside the app."

But even with that concession, both the Journal and e-book seller Kobo have decided they do not want to give Apple a 30 percent cut, and they are not allowed to include a "buy" button that links to an outside website. A spokeswoman for the paper said that Apple's rules "would create a poor experience for our readers, who would not be able to directly manage their WSJ account or easily access our content across multiple platforms." Now, customers will need to call customer service or visit WSJ.com to subscribe.

For Kobo customers, digital books will be available through the Safari Web browser by visiting kobo.com. Users will still be able to access and read Kobo-purchased books from their library on an iPad or iPhone.

In addition, Amazon on Monday also updated its own iOS application, with version 2.8 removing the Kindle Store button from the App Store software. Like with Kobo, Kindle users must purchase their content from elsewhere, like the Safari browser or even another device, in order to read it on their iPad.

Barnes & Noble, too, updated its own Nook application and removed a buy link. Users are instructed to visit nookbooks.com in their browser to purchase new content.

In addition to the Journal, Amazon and Kobo, the Google Books application may also have been affected by Apple's newly enforced restrictions. The software is no longer available on the App Store, but a spokesman for the search giant reportedly declined to comment.

Apple's change of opinion in June came soon after one prominent newspaper, the Financial Times, decided to create an HTML5-optimized website rather than submit to Apple's in-app subscription rules and give the company its 30 percent share of sales. The paper's application was highlighted in 2010 at the WWDC Apple Design Awards.