Is this a subscription?

No. You "purchase" alfons once, meaning you acquire the usage rights and can work with the program for as long as you like.

With alfons pro and alfons kit, all updates are free for one year from the date of purchase. After the year is up, you can freely decide whether you simply want to continue working with this version or whether you also want to benefit from future updates. Extending the subscription for another year costs 50%.