Simple, transparent, and completely offline licensing.
The Free Trial provides exactly the same technical capabilities as the Pro version, restricted to 14 days and a single user for evaluation.
Pro keys are bound to your hardware. If you upgrade your PC, you can easily deactivate the old instance in your dashboard or contact support.
As long as the hardware stays exactly the same, the OS reinstall will not invalidate your hardware ID.
Since Pro is a perpetual license, you keep the version you bought forever. The renewal key just gives you another 12 months of major software updates.