If you are trying to install the Vuforia SDK on your Mac and you are running the Mountain Lion OS, you might get the following error message (or similar one):
"vuforia-sdk-xyz" is damaged and can't be opened. You should move it to the Trash.
This error is typically due to GateKeeper, which needs to be disabled, by going to:
Preferences > Security&Privacy > General
and unlocking the key and allow applications downloaded from "anywhere".