Fingerprint SDK is distributed with a trial license valid for 90 days*. After this period you have to buy a license to keep using it.
Check the Griaule Web Site for licensing options, pricing and instructions on how to request commercial licenses.
To know how to apply and deploy licenses, check the Licensing Fingerprint SDK Based Deployed Applications section.
The trial licenses of Fingerprint SDK are for non-commercial use. There is no technical limitation: the only difference is the splash screen displayed when the library is initializing.
* Note that after 90 days the library still works normally, but using it without a commercial license will be an explicit violation of the license agreement. To use the commercial license there is no need to reinstall the SDK; you just have to proper replace the trial license with the commercial one.