Server products and apps are hosted on your servers. This app is sold as a perpetual license, and the purchase price includes 12 months of maintenance (support and version updates).
You can renew maintenance after 12 months at 50% of the current purchase price. You can upgrade the tier of your Atlassian product and app licenses at any time. Upgrade prices are calculated based on Atlassian's formula (view example).
If app pricing changes after your initial purchase, there's a 60-day grandfathering period during which you can renew based on the old pricing.