Differences between Arma 2 Free and Arma 2 Demo

Trying to find more information about the DayZ mod, I learnt that the base game (Arma 2) appears to have 2 different 'free' versions, one enticingly labeled as 'Arma 2 Free' and also a seperate 'Demo' - however neither the official site nor Steam helped me figure out why anyone would go for the demo version.

To make things more confusing, the Steam download link for Arma 2 Free says 'Download Demo'. I'm aware that demo release was 2009 and Arma 2 Free was 2011; and the features not included in the free version.

So, what is the demo - and does the Steam download for Arma 2 Free actually install just the demo or the full 'Free' version that I could get from the developer's site?

According to this page, the free version is mislabeled as a demo. So the "demo" is actually the free-version.

The difference between ARMA II and ARMA II Free is that Free has lower quality audio/textures, and doesn't have the single-player campaign.

Also, according to this page, ARMA II Free can be used to play DayZ Mod (you still need to purchase ARMA II: Operation Arrowhead). That page also confirms that you get ARMA II Free using the "Download Demo" button in Steam:

Users on this page have confirmed that DayZ does indeed work with ARMA II Free.

• Yes you can in fact download Arma 2 Free and buy Operation Arrowhead and install it to Arma 2 Free. Then you can already play [DayZ]
• The free version has low resolution textures but people say it will work. Remember, there's no support for the free version, so if something goes wrong.. well you're kind of on your own.

The demo on Steam is Arma 2 Free. If you search Arma 2 Free on Steam, you'll notice that it brings you to the Arma 2 page. The only free download link on that page is the demo link. You'll notice when you click Download demo, it begins installing Arma 2 Free. It may have been something different before 2011.