OpenVPN's activation system requires an internet connection for subscription keys, making it easy for the company to detect and revoke illegitimate keys.
While the software allows two connections without a key, you can also obtain a specific "Free Subscription" key by registering on the OpenVPN Access Server Portal 14-Day Free Trial: Openvpn Access Server License Key Free
OpenVPN allows you to use Access Server for free with the following limitations: Openvpn Access Server License Key Free