Currently you have to be a member of their affiliate program to get API access. To become a full "member" you have to be a prospect who generates three referral sales (iirc) within a 30 day period. So once in you have the API, but getting in isn't as easy as filling out a form. From there you can get your API rate limits increased from the default 1x call per second up to 10 based on your prior 30 day affiliate sales.