Is the Free version of Avast really free or is there a limit?

I just downloaded Avast Free version and I wonder is it really completely free? It seems like there’s a limit 60 days or something like that, it also seems like I have to “register” or something… Can some one here please help me out?

you can use it for 60 days without register,
when you register you get a free 1 year license, and this you have to repeat every year

Installation Guides and Manuals http://www.avast.com/eng/download-user-guides-and-manual.html

avast! 4 FAQs http://www.avast.com/eng/faq-avast-4-home-professional.html

Register your free product http://www.avast.com/eng/home-registration.php

How to insert activating key http://www.avast.com/files/tutorials/insert_key.htm

download http://www.avast.com/eng/programs.html