This is a trial version, available for 3 months from the time of installation. It is fully operational, with one exception: The "Backup" feature of the database is not fully operational.
If you decide to buy the full version, simply purchase and install "Customer Manager Unlocker" . As long as the unlocker remains installed on your device, all features of Customer Manager will work fully, without any time limitation. All of your database that you will have built up during the trial period will remain intact.