I have seen an commission junction and other affiliate networks the phrase that a sponsor will not tolerate direct linking? Is this referring to using their server for ad image hosting or to using redirects/ using their URL as the direct destination of an paid ad?
Direct linking is usually associated with PPC (pay per click advertising) such as AdWords. Direct linking is when you link directly to the parent affiliate website. So when someone clicks your ad they are sent directly to the affiliate site (no landing page). Some merchants don't allow this while others do. I have a guide below in my sig about PPC and direct linking feel free to read it Thanks.