On the download page, the (*) column tells you if the application is free to use (F) or comes with a trial license (T)
Clicking the (T) gives you an overview of the license options:
After starting the application for the first time, you will be prompted to request a trial license.
This trial license allows you to test drive the application for a specific time (usually 30 days).
If you already have a license key, you can press the "Enter License Key" button and enter your license key.
When you are satisfied with how the application works, you can go to the help/about(*) menu and press the "Register now" button.
This will open a secure webpage where you can enter your registration details and purchase one of the license types.
After completing the registration steps, a license key will be send to you by email.
(*) The exact path to the about window can differ per application
You can now enter the license key that you recieved by email. Press the "Refresh" button, and your license is registered.
Some applications are free to use, others come with a trial license that allows you to test drive the application for a specific time.
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