If a freely available piece of software doesn't ask you to pay ('nag-ware'), or disable features/stop working ('cripleware'), or include piggyback software ('whoreware'), then it can hardly be considered shareware. It would be more like 'donateware'. If there is no incentive to pay, then why would anyone do it? "Moral people", you say? Well guess what.. there aren't that many of those around.
Take this scenario for example: A car dealership has a promotional deal going. You can come into the showroom, choose any vehicle you like, and drive it away without paying a dime, no strings attached. So you go in, choose a brand new Porsche Carrera, climb into the car, fire up the engine and drive off. Would you get out your wallet and pay for the car? I kind of doubt it. What if everytime you started the car, a recording blasted out of the speakers suggesting that you pay for the car if you feel like it? What if the steering wheel fell off after exactly 15 days? What if a salesman from the store always sat in the passenger seat trying to sell you additional cars? Would you be more inclined to pay for the car, or would you take it back to the dealership? That is how shareware works. If none of those annoyances were present, the car would be free (though you would be welcome to donate to the factory workers who built the car).
You said that you bought AVG Pro. Sure you can get it for free, but I know for a fact that AVG free is 'cripleware'. Several features are disabled/removed from the free version, and are only available if you purchase the professional version.
-genius_at_work
