§9 (rules of the game)
§9 If a player logs into an external account without the consent of the owner, this leads to the deletion of the own account. Guild theft/guild dissolutions through mergers are also punished with account deletion.
So you (of course) violate the rules of the game if you hack into an account and cause damage (selling equipment, etc.). If a whole guild is taken over by a merger, e.g. by kicking the former guild leader out of the guild, this also violates this rule.
Info: The first point is: If the password was so insecure that even a child could have cracked it (prime examples: 123456789, asdf and CO.), it looks bad with compensation for the damage! (Safety Instructions)