Yes, they are very legal, just Blizzard does not like them, because they take their money.
There are no GM power hacks on retail (legal) servers. There might be on private servers, but private servers are illegal. We can not help you with that here.
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.
No.
You can not play World of Warcraft for free with out downloading it. WoW is a client-server game, you have to have the client installed in order to play. While there are free private servers available, they are not legal, and are usually pretty buggy.
They are against the ToU, and will get your account banned. Plus blizzard can take legal action against you.
That's impossible, ALL Private servers are Illegal, i would suggest staying away fron them.
No they're perfectly legal.
In the strictest legal terms, WoW servers are not legal, since they require a (basically) hijacked version of the official server software to run, which is not the property of the people running the servers.
Strictly speaking, Private Servers are not legal, since you are essentially using a pirated version of the server software required to play the game.
Everyone who plays WoW on LEGAL servers are regular users. The only people with admin rights are the GameMasters (GMs). GMs are PAID Blizzard employees who look after the system.
Yes Private Servers are legal to play but there against the copy right as along as you delete your cache before you go back on retail they won't even know you were ever on one so yes they are legal but if you get caught they will ban your account and ban your IP address but you always can change it
Yes they are against the policies of Blizzard. Further more, they could also be considered illegal law-wise. They could be considered stolen property.