Even as a XF license holder, I really find it hard that XF has even ranked as high as it has in this poll. While a few aspects are are nice about XF there are still many missing features that are just not found in other commercial products, plus not counting XF is all but dead. Who exactly is working on XF right now and how far along are we until we see an update?...
People vote for what/who they know (many competitions are rarely about the product, but more about the number of "friends" you have)
Forums that have been around for a while will gather lots of users
Free forums will gather lots of users
Since burning board has a lite version, which attracts lots of "free" users
And the options don't include "burning board lite" + "burning board commercial" .... you're going to get a lot of users clicking for Burning Board comercial, since they use the free version
Looking at the 'Featured Forums' for Burning Boards, it looks like a lot of universities use the platform. They are highly likely to be active boards with students checking them out on a daily basis and if the posts are in the right place, votes will be cast for the platform.
It's great to see that XenForo is up in 4th though, that's a good achievement to say that the software isn't very mature or fully developed yet (although it is stable). We all know vB shouldn't be at second though, but they have years behind them and a huge customer base too!
xenForo was number 1, xenForo is number 1 and xenForo will always remain number 1. People just don't realize good things until they get hit on the head with dirty underwear. In this case vBulletin is the dirty underwear. I know I didn't make any sense, blame vb 4x.
I never had a script in 2012 but far as I'm concerned there's really only two great forum scripts, Xenforo & IP Board. I'm a newbie but still have 3 licenses each to play around with and occupy my time.