There are no non-profit or even strictly business-related terms under the umbrella of the App Store as far as I know. There are no corporate/business iTunes purchasing accounts, no escalation to root-level privileges allowed for apps in the MacAppStore(postponing backup and other more powerful apps). This seems like another oversight on Apples part due to treating it as a lower priority.
And although they have every right to be proud of their achievements, it seems a bit like "you owe me" to remind Apple that they used the Apache-licensed Readability tech for Reader. Their proposed app could stand on its on.
What you're missing is the other rules which force you to offer purchase via IAP because you offer subscriptions outside the app, too. The following terms apply:
11.1 -- Apps that unlock or enable additional features or functionality with mechanisms other than the App Store, except as approved in section 11.13, will be rejected
11.12 -- Apps offering subscriptions must do so using IAP, Apple will share the same 70/30 revenue split with developers for these purchases, as set forth in the Developer Program License Agreement.
11.13 -- Apps can read or play approved content (magazines, newspapers, books, audio, music, video) that is sold outside of the app, for which Apple will not receive any portion of the revenues, provided that the same content is also offered in the app using IAP at the same price or less than it is offered outside the app. This applies to both purchased content and subscriptions.
11.14 -- Apps that link to external mechanisms for purchasing content to be used in the app, such as a “buy" button that goes to a web site to purchase a digital book, will be rejected