The only thing that could be an issue with using the BBC app on a DAP is most of BBC’s content is country specific (I.e. can only be used in UK) and DAPs aren’t country specific. But, as long as you can log into the app on the DAP and stream when you have WiFi downloading for offline use wouldn’t be an issue.
Regardless, as long as you can use the app on the DAP to access BBC content when you have WiFi downloading for offline use would be no different than with a cellphone with WiFi/data turned off.
Regardless, as long as you can use the app on the DAP to access BBC content when you have WiFi downloading for offline use would be no different than with a cellphone with WiFi/data turned off.