I recently had a chat with a GM about Addons that require you to put files/edit files outside the WTF and AddOn (for example the "sound" "data" or possible subfolders of Interface) folder. According to the GM this was abolutely forbidden and bannable according to the ToS:
You agree that you will not, under any circumstances:
D. modify or cause to be modified any files that are a part of the Game Client or the Service in any way not expressly authorized by Blizzard;
That is because those "AddOns" are capable of editing any texture/sound or client file. For example the fishing bobber sound, the Blizzard default UI elements, the player/mount/npc/weapon/armor models and other vital parts of information used by the client.
I have so far found several such "AddOns" downloadable here so I was wondering if there's any official position from WoWI on such mods since they violate the ToS?