Apple’s in-app purchases policy has forced some changes to the apps of the Wall Street Journal, Kobo, Amazon’s Kindle and Barnes and Noble’s Nook. If you’re interested in purchasing an individual e-book or subscription from any of those apps, you’ll have to do it through the Web or by phone, because you can’t do it from inside the app anymore. The Cupertino, Calif., company announced in February that it would be restricting in-app access to other stores for any apps purchased from the Apple store.