Is integral WoW a legal private World of Warcraft server

All private servers are "legal" in that they are not breaking any laws.

However, Blizzard considers private servers a violation of the Terms of Service of World of Warcraft in general, and therefore, any private servers are actually in violation of Blizzard Entertainment's Terms of Acceptable Use for their software.

In other words, private servers are like pirated software, and you should always be careful to be sure your username and password on a Private server NEVER matches any other username/password combination you have elsewhere online.