The Viewer module works in trial mode for 30 days. In order to use the program beyond the 30-day trial period, you must register the Viewer with a valid license key. To obtain a free license key please refer to this free license key generator. The license key will be sent to your email address. To register the Viewer with the free license key, please, follow this tutorial. Other program modules such as Host, Agent, and RU Server do not require registration.