You can pay just $5 a month and use our cart on as many websites as you like. Our system doesn't lock you down to any one domain or page address.
By that same note, there's no way for our system to tell which of your four different websites the order is coming from, so our cart will be displaying the same logo and business name to your buyers regardless of the site they are on. If that's not a problem you've got nothing to worry about. 
