Its clear intent on the part of the programmer who wrote the code, in my opinion. They obviously designed it to modify webpages, and its not doing anything out

Its clear intent on the part of the programmer who wrote the code, in my opinion. They obviously designed it to modify webpages, and its not doing anything out of the ordinary or unexpected when its modifying GPL'd webpages. Just because the programmer didn't consider that there may be licensing restrictions attached to modifying web pages doesn't mean that they should be exempt from them.