When I first started developing RSW I tried to get in touch with die.net about using their images for such a cause but I never got a response back from them. So, I continued using the images on the grounds that the images are free to use as stated here, as long as I provide a link back to their website which I did.
I already send them a message about this problem and waiting for a response. I'll try to get an agreement with them and see if I can sort this out asap.
I'm also looking at other alternatives, like using a http request within RSW instead of using wget or perhaps download the images to an external server and use the images for RSW from there, but any changes will take some time to develop specially now that I have exams coming before Christmas, etc...
The bug on relation to this can be found here.