[rsweares]

I paid for the app for my iPhone, why do I have to pay for it for my iPad????

[dano]

You don't have to pay for it twice. iTunes knows that you have purchased the App originally (assuming that both devices are in the same account on iTunes). If this is the case, then it only appears that you are being charged, when you first install from the iPad.
After installation, set your devices up as outlined in the "GB Help" thread.