Is there really any harm in using concepts put forth by a video game in the creation of your own game?
I mean, Minecraft is similar to Infiniminer, GTA IV is like JC2 is like SR3, Assassin's Creed is like Prince of Persia... The list goes on.
It's not copying, it's inspiration.
Hold on a second.
The games you listed and their similarity are different then my view on this game and DayZ.
If i am wrong, please, do correct me.
The games you listed, are indeed inspired by the other games.
However, WarZ seems a very lot like DayZ.
In fact, as far as i can tell, it is like DayZ in ways of gameplay.
They just did some fancier/other graphics and used a sort of MMORPG way of releasing parts of the world.
What matters is that games can indeed be inspired by other games, but for them to be inspired by other games (and not being a plain copy), the gameplay needs to be different.
And that is what i and some other people, fail to see here.