Bitdefender may "require" that free account, but you don't need to do anything with it. Just register the install, and forget about the registration. I've never received a single email I didn't sign up for, and it seems to be the most useless feature, unless you happen to want one of the services offered when you complete your registration. I almost ignored it, but when I first installed it, I figured I'd see if that was a problem. Turns out there was no harm done, and no real gain... outside of being able to use the AV normally lol. I think it's pointless, but that's probably there for some half-assed reason.
And yeah, Avira is pretty lavish with ads, I hear. Makes me laugh at the people who switch from Avast to Avira, and vice versa, because I've seen so many users switch between the two, and claim one is way better than the other, and how there's "less ads" on one of them. I swear they're probably made by two companies founded by guys who were room mates. They both seem to have the same cult-like followings, both offer reasonable protection (nothing outstanding), and they both try to badger you into buying something. Yeah, they're totally different lol. Humans make me giggle.