How to put a demo on your site
For commercial sites, it is advisable that you become an affiliate. If you are an affiliate, you'll get a commission for each completed sale that was referred to by you.
For more information, see the Affiliate info page.
If you have a personal site, you also have the option to sign up as an affiliate. Probably a better option though, would be to become a promoter. As a promoter, you'll get VIP-points and a badge next to your name. You can also get free licenses to give away to your friends.
For more information, see the Promoter info page (members of this site only).