Hi,

Apple cleary states the guidelines on what you can and what you can't sell on appStore from this guide: https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/StoreKitGuide/Chapters/Products.html#//apple_ref/doc/uid/TP40008267-CH2-SW2

IAPP basically applies to content or services WITHIN your app, say you want to enable content, like on games, or what to enable services to access some data within your app.

For the sample apps you gave, they dont need to have IAP within the app since they are offering a complete system which includes Admin and backend portal. The app is just a client that the system will use. You control transactions within the back end. Either you can bill customers based on trasactions made on the app, or based on subscriptions. In app purchase is good if you are developing iOS ONLY app, and dont want your users to log or use in any other systems, but if your developing a complete system where users will log on their admin account, see reports, pay bills, and most specially, if you want to own 100% (apple gets 30% for every earning you get on IAP) of your earning from your transaction, you can avoid using IAP.

For your second question, the reason is that, this app is published using an Enterprise account. If you are a company, you can signup for an Enterprise account instead of the normal developer account. What differs from an enterprise account is that you dont need to published it on iTunes and hence does not follow the normal app review process from apple. That means, you can develop any features you want without violating any guidelines that apple have set in publishing your application. Enterprise account is suited for company and organizations who have their own set of policies. Donwloading an app from an enterprise account needs users to trust on the settings, thus downloading from an unknown source is risky.

Hope the information above helps. If you have any more follow up quetions or any queries regarding your iOS app development, you can always book a call and I will attend to it dligently.

Warmest Regards,
Francisco