I know it can be little confusing and annoying when you want to purchase a free products from this online shop.
To purchase free product, don’t click PayPal/payment button. Instead, click Add to Cart, then click View Cart/Checkout. There you will asked to login/register, then you can download the files.
Do you need to register and login to purchase? Yes of course, you need to do so, then later when you come back to this website again you can simply login and re-download your purchased assets.
Cheers… Hope that helps.