I am at work so I can't check, but I believe that the free license for Internet Security 2015 requires 2500 points. I thought it said that in the "Account" tab inside the Avast control console/panel.
You get 250 points for getting one person to use your download link, and I am willing to bet that the catch is that the person needs to register the free copy with their email and use it some.
However, the rewards page on my.avast.com clearly says that getting seven people to install Avast downloaded using your personal link will earn you a license for Avast Internet Security. Seven times 250 equals 1750 points, so things are not entirely clear or consistent.