The license is for channel (ACTi video devices) to work on NVR 3 Enterprise.  The number of add-on channels supported: 1-184 (NVR 3 Enterprise), 1-136 (INR-420), 1-32 (INR-320, INR-330). Price listed is for single channel add-on license.
NVR 3 Enterprise: The software NVR with support up to 200 cameras or video encoders; Smart Search; Export video; Event management; e-Map; free license for 16-channel ACTi and 1-channel third-party video devices included.