Hey there, guys!
Just to let you know - if you have the "Can't open the application" issue on your iMac / Macbook just follow these steps:
Open Terminal and get to your World of Warcraft folder:
cd Wrath of the Lich King 3.3.5a (Mac)
cd World of warcraft.app (not the launcher)
cd Contents/MacOS
sudo chmod +x *
type in your password
Launch your World of Warcraft.app
Thank me later :)