You are free to use Awasu indefinitely.
When you [purchase] a copy of the Advanced or Professional Edition, you also receive 2 years of free upgrades. We are constantly working to improve and add new features to Awasu and release new versions both regularly and frequently. You are entitled to receive these new versions for 2 years after your purchase date and we hope that you are happy enough with Awasu to purchase another 2 years of upgrades (at a reduced price) when the time comes.
However, even if you don't, you can still use Awasu for as long as you want. We don't like subscription-based software any more than you do. You paid for it, you can use it.
The only exception to this are alpha releases which have an expiry date. These are bleeding edge releases intended for people who want to have a play with new features as they are being added. They are temporary releases and are not intended for general use. However, a new release will always be made available before they expire.
[Trial versions] of the Advanced and Professional Editions are available and are fully-functional, time-limited versions.