Now, I agree that it's probably a violation of the actual wording of the EULA, but I don't think it qualifies as "illegally warez multiplayer".
People who are running this have purchased their licenses to play the game.
I just read through the "Restrictions" section on the License Agreement, and its wording regarding things of this nature is somewhat vague. It seems to be prohibing things like copying the software, selling unauthorized add-on packs, and modifications in the vein of "cracks"...things of that nature.
I wouldn't be entirely sure if this qualified.
At any rate...
I have yet to get the multiplayer aspect to work, but I haven't really tried that much.
The utility itself, however, is pretty slick, and offers a number of useful functions for customizing your gameplay experience.