For licensing we abide by the standard Apple and Google terms of service.
Summary
Personal use at home means you only need to buy one copy of each app for all your devices.
Business use with multiple staff members means you should buy a copy of each app for each device.
Details
1. If you are using the apps for personal use and you have multiple devices, say a phone and a tablet or two tablets, then you only need to buy one copy of each app and you can use the same account to download the app to all your devices. You may also be able to use the Family Sharing program to share the same license with other people living in your house.
2. If you are a business or speech therapy department and have multiple devices that are shared by multiple people, then you should buy a copy of each app for each device. For example, if you have five iPads that are shared between ten members of staff, you should buy five copies of each app, one for each device. Each device will need its own Apple ID to do this.
The Apple terms of service are here: https://www.apple.com/legal/internet-services/itunes/us/terms.html
This is the relevant section:
"- Individuals acting on behalf of a commercial enterprise, governmental organization 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 license."
The Google terms of service are here: https://play.google.com/about/play-terms.html
This is the relevant section:
"Restrictions: You may not:
– use Content as part of any service for sharing, lending or multi-person use, or for the purpose of any other institution, except as specifically permitted and only in the exact manner provided."