I've seen a few threads about this, and one even here on mmo-champion. People were saying it's okay to use, but blue just confirmed it's against the rules. I wouldn't suggest using it, if you were planning on it.
http://us.battle.net/d3/en/forum/topic/4916891761
https://twitter.com/#!/Angryrobotics...05207039578113
Eh, messed up title name. It's DarkD3, not D3dark. My apologies.
EDIT: Good news! You might be able to use DarkD3 afterall!
http://twitter.com/#!/Angryrobotics/...26183740686336