IFRAME
I believe it is widely held that the owner of the site where the image file resides is responsible for rights to the image.
HOT LINKING
Below is an example of another way that I can show content on my page that actually resides on another page. This is called hot linking. We are simply displaying an image file that is actually resident on your website. Again since we are not uploading a file, but just sharing content that is offered freely for public consumption, I don’t believe we are required to obtain a license.