ios app for membership-based organizations

[Richard Miller]

Looking for suggestions on how to structure an iOS app that is free, but can only be used by members of a particular organization.

For example, an app provided by a bank can only be used by account holders at that bank. The app is free through iTunes, but it is useful only to members who can enter a verifiable access code (ie bank account number).

Let's say I want to build a similar app for an organization like Greenpeace, designed for its members. Those members don't currently have a membership ID, as would be the case at a bank. But the app could request an email address and then confirm that that address is contained within the Greenpeace membership database. Once confirmed, the free app would be usable by that individual. Would Apple have any issue approving this app structure?

Let's say that Greenpeace chose to distribute specific access codes to its members that would be used to unlock this free app (as opposed to using email addresses). Would Apple be okay with this structure?

Thanks
Richard Miller