Any FREE version of the OfflineSurveys Android app can easily be turned into a fully featured PRO version by simply entering a license key. You only need to purchase 1 key even if you are running OfflineSurveys on multiple devices because once the key was entered, the whole Limesurvey domain you are using will get unlocked for all devices.
That also means that while you can use one license key for unlimited surveys, responses and devices, it is only valid for one single domain.

Getting your own key is pretty easy:

  1. Select the desired license duration.
  2. Click the Paypal check out button (Paypal supports credit card payments).
  3. Pay using Paypal.
  4. After Paypal has reported a successful payment, an email including your license key will be sent to your Paypal email address.
  5. Finally, just enter the key at OfflineSurveys (there is a key icon top right at the app) and you are done.