You can Check Your Activations on the Radmin Support Center to see how many of your licensed slots are still available. Step 2: Online Activation (The Fast Way)
(if you cannot buy Radmin)
The company has moved on to Radmin 3.6 and now Radmin VPN and newer commercial versions. The official support lifecycle for Radmin 3.5.2 ended several years ago. This means: radmin 3.5.2 license file
Technically, Radmin uses a registry-based activation system. When you enter your license key into the Radmin Server, the software communicates with Famatech’s activation servers. Once validated, the "license" is stored within the system’s configuration. You can Check Your Activations on the Radmin
: A standard license allows up to 5 simultaneous connections to the server. radmin 3.5.2 license file