The license is a perpetual license. One license key allows you to use the app indefinitely. You are also eligible for one year of free updates.
If you don't want to renew your license after one year, you can continue to use the last version of DevUtils that you have for as long as you want.
You can renew your license here with a 40% discount for another year of updates. That means the renew price is 60% of your purchase price (before discount) and won't be affected if the app price increases in the future. (e.g., $24 for the Basic License)