If we find out that you downloaded EFT on a pirate website you'll be banned without further informations.
You need to own the game and keep it installed on your computer to play AKI.
Lets you put folding stocks on AKs that normally wouldn't be able to take them. You can now put skeletal triangle stocks on the Saiga, AR-15 stocks on the AKS-74/AKS-74U, and all that good stuff or something.
Advanced Custom Weapons probably already does this, or at least, it should. Don't install if you're already using that or something.