The word “Free” has gone through a transformation since the introduction of the Internet. Today, software and game makers use it all the time for their stuff. “Download our game for FREE!” Though, what they don't tell you is that you won't be able to play the full game with the FREE version.
Survey software makes you do the same thing. They will offer FREE Survey software as a watered down version of their program. However, if you want all the bells and whistles you'll have to pay for it. The benefit here is you can try out a bunch of different versions until you find the one that's right for you.