You can only request 1 key per distribution platform from an IndieGameStand account. When you purchase additional copies and do not input a gift email address, we will email you additional IndieGameStand.com keys that can be redeemed on our website by your friends. All you have to do is email them the key and/or link and they can setup an account and unlock the game in their IGS wallet. From their wallet they can request Steam, Desura, GoG keys.
These keys are also stored in your game wallet. An "Extra Copies" button will appear for any games that you own multiple copies - when you click this button it will display your unused keys that you can gift to friends.