License activation only online?

In our project we want to use the Astra Pro in combination with Unity. Since the endproduct is going to get shipped to remote locations we wanted to buy licenses, but on the product page for the license keys there is a concerning statement:

An Internet connection is required for activating the license.

Does someone know if this is only once required (simillar to a windows key activation)? Or is a internet connection required all the time?

Thanks for helping!