Setting up the codes for your third-party partner to issue would be similar to setting up Gift Coupon codes as explained here, just without performing the last section about setting up a Gift Coupon product to sell those codes:

http://www.e-junkie.com/ej/tips.gift-coupons.htm#online



You can obtain the bare link URL from your product's E-junkie Add to Cart button and have buyers referred/redirected directly to that URL, which will bring up the cart with that item already added to it:

1http://www.e-junkie.com/ej/tips.button-code.url.htm1



Perhaps better yet for your purposes, you can include a Discount Code in that link URL itself, so if your third-party partner can dynamically append each buyer's code to the URL they're referred/redirected to, that would bring up the cart with the item added to it AND the discount pre-applied to grant access to Free Checkout for placing their download order:

http://www.e-junkie.com/ej/tips.discounts.in-button.htm



Finally, bear in mind the number of Free Checkouts (orders with a 0.00 order total) you can accept per day is limited according to your subscription plan level, though you can temporarily upgrade to a larger plan at any time if needed to handle a spike in Free Checkout orders:

1http://www.e-junkie.com/ej/free-checkout.htm1