Zygor has definitely been a topic of discussion on this subject. Blizzard doesn’t give any official comment on addons, but given that Blizzard is probably well aware of them for many years and they are still operating, I’m inclined to believe that they toe the line, but don’t cross it.
Regardless, the only way to ensure Blizzard knows is to email hacks@blizzard.com and let them investigate. Don’t be shy about it. It’s not a bother.