Hi brikan,
Sure, avast-Home is free. If you check your "About avast" (right-click the ball icon), you'll see that the license for the program itself is permanent, but for renewals it shows experation date (and time, right down to the second
) which is a year (actually more like 14 months) from when you last registered.
Re-registration is free, just like the original -- just register again
here and you'll be emailed a fresh registration code to plug in which is good for another year. Note you can do that any time before (or for that matter I imagine even after) your registration expires.
Best,
Mike