Here are Plugins & Snippets collection of downloads related to Affiliate Marketing. Please have a look if there's any download that could be of help to improve and enhance your Easy Digital Downloads WordPress webstores.
Affiliate programs are more difficult to set up for a digital product marketplace. A good affiliate program pays between 25% to 50% of the ticket price to its affiliate marketers. All you can do is to pay affiliate marketers a percentage based on your commission of 20%, therefore reducing the absolute amount you can offer to affiliate marketers down to maybe $3 to $5 per sale.

Source: How to Build a Digital Product Marketplace in WordPress - Plugins & Snippets