I am NOT an expert on copyright infringement laws... but, I thought that if you used an image you found on the internet that you are supposed to cite the source material.
In my latest post I used 3 images from the internet (the 2nd, 3rd, 4th images in the post)...
When I wrote the post, I simply copy and pasted the link to the image's URL. Which, explicitly cites the source material.
BUT!!! A few minutes later, discourse copied the 3 internet images over to the flow server and used a copy of the image in the post without providing a citation to the source material. Correct me if I am wrong, but, I believe that this is not an appropriate way (i.e. not legal) for discourse to behave.