I wouldn't have recommended it if it wasn't free :)
What they're selling is actually a "priority support account." I have no idea what this does or why you would want to buy it, but all of the software itself is actually free.
My best guess is that it's something you'd want to use if you were a business, if you've got defraggler deployed on 300 work stations and it stops running for some reason, $34 a year is a bargain for support when you consider actual labor costs.