4Mata allows you to use the full product for a period of 14 days for free.
A Subscription number is not required.
How does a Solo subscription work?
4Mata makes requests to the subscription server to confirm the validity of the subscription key provided by the user to activate the subscription.
How does a Pro subscription work?
When 4Mata starts, it requests a floating subscription from the subscription server. The subscription server checks the number of available subscriptions with itself; if it finds a free subscription, it leases it to your app for a specified amount of time.
After the leased time is over, 4Mata automatically sends a refresh request to the subscription server to extend the lease, and the process repeats itself. When your user is done using the app, it sends a request to free the subscription, thereby making it available for other users.
It should also generate a unique device fingerprint and send it along with the subscription activation request.
The subscription server stores the device fingerprint and uses it to validate the subscription key for further activations to prevent the subscription key usage on other devices.