No, there is no api for our Marketplace. 

The vendors own the copyrights to images and products, so typically they shouldn't be used. However,  we make an exception for Renderosity affiliates who link to the product pages for sales, and have no other questionable or illegal activities on their site. (like file sharing). 

Site scaping and web crawlers depend on exactly what you are doing. Anything can cause a "disruption of normal site operations" could be TOS violation, so just be careful that anything you do doesn't create a load on the system or cause problems (like a dos).