In the following link you will find the license agreement of NUIA:
The license agreement is user-related. Each user can install and use NUIA on 3 different devices.
For your respective mounted eye tracker, please refer to the manufacturer's license agreements. E.g. for a Tobii eyetracker you can read the license agreement in the following link:
https://www.tobii.com/xperience/temp/terms-of-sales/