OK, so I typed in the threrad ID in your screen shot, and I came to a thread with a blue poster saying this :

"Dual-Boxing as far as I am aware is not illegal, I sometimes play more than one copy of the game on my computer at home, when I need to run through a low level instance or help out on a difficult group quest.

The only thing that is not legal is the use of bots or automated scripts to control all these characters, this if discovered could get all of your accounts banned."

Therefore, I would not be over worried