A portion of the Terms and Conditions states the following;
- If you are an individual acting in your personal capacity, you may download and sync an App Store Product for personal, noncommercial use on any iOS Device you own or control.
- Individuals acting on behalf of a commercial enterprise, governmental organisation or educational institution (an “Enterprise”) may download and sync Apps for use by either (i) a single individual on one or more devices owned or controlled by an Enterprise; or (ii) multiple individuals on a single shared device owned or controlled by an Enterprise. For the sake of clarity, each device used serially or collectively by multiple users requires a separate licence.
In basic terms
Individuals at home: You need to buy one license of an app per iTunes account and can then use that app on all of the iOS devices you own or control and sync with that iTunes account.
Commercial enterprise or educational institution: You need to buy one license of an app for each iOS device if that device is used by multiple users or one license of an app per user if that user is using multiple iOS devices.