Well you're uploading the image link, so even if the link was added it would just be a link straight to the image. The site would have no way of knowing where you got the image link from.
Here's an example in case this isn't making sense (fake links are much smaller than they would be but you get the idea). You go to pinterest and find a pin. That link is something like pinterest.com/pin/12345678. However, the image address you use to upload items is something like i.pinimg.com/87654321.jpg. Urstyle has no way of knowing what the original pinterest link was.
You can always copy the website link to the item description though.
... Read more