First, you DO NOT need to register this app to try it. When you open the app, and it asks you to register, click on the "register" button. iCal will open up, and then an open dialog box will open, to let you select the license key file, just click on cancel - and you'll be able to test out the app. I don't know if there is a time-limit on this method or not, of if any of the apps features have been disabled...but it at least allows you to test it out.
For the most part, a great little app...easily lets you add events to any calendar weeks, months, or years in advance without having to go to that date in iCal. A couple of things though, one better documentation for sure (though it isn't hard to figure out) and I wish it didn't have toa ctually open up iCal to work.