Interesting.... this page says "This is a free update for all licensed owners of Airfoil for Mac, so all existing users should simply choose Check For Update from the Airfoil menu".

In fact, it is not a free upgrade for all users of Airfoil for Mac. I have Airfoil 2.0.6 and it's a paid upgrade for me - $10.

Not a big deal, but you may want to correct the language on your web page.