Our licenses are perpetual.
The license fee is a one time payment, no subscription.
You will receive a perpetual license for our current version 9.
Once a new major version (with new, additional features) gets released, you can either upgrade at a (discounted) upgrade rate, or stay with your version.
We also offer Upgrade Assurance ("2 Years Upgrades and Support"), which would include those upgrades as well. Upgrade Assurance can get renewed every second year, so this would be the only cost to stay up to date with our latest versions at all times.