It's possible to convert a NoMachine server for evaluation to a server for production by simply activating the customer license file suitable for that type of server.
 
The license must be suitable for the OS where the server for evaluation is installed and be of the same type of server product (server type and license type must match).
 
If not, you need to uninstall the evaluation software, remove the installation directory if still present and install the NoMachine server package downloaded from your Customer Area.
 
To install a customer license (server.lic) v8:  https://kb.nomachine.com/AR04T01157