A: When you purchase a plugin from Oxwall Store you are granted license key for it. When you try to install a paid plugin (Admin area → Plugins → Add new) you will be asked your license key.
If you use it for the first time Oxwall Store will remember IP address from which you apply this plugin. That IP address will be remembered from now on and the plugin will refuse to be installed from other IP addresses.
When there's a plugin update available you will also be asked for your license key when upgrading. The update also needs to be performed from the IP address on the record.