Quote Originally Posted by BokoToloko View Post
Terms of Service means the set of rules the company sets in order to use their products, where they're within rights (right you grant them by agreeing to their ToS) to sanction your account or outright ban it as they deem fit.

Mods aren't illegal but they're not allowed either by the company and, if they decide to ban you over them, you'll have little say about it.
Not entirely true, the modification of either soft or hardware is highly illegal in japan. You can get serious jailtime for that. That said in most western countries it is not illegal.