Multi client rule has been updated a bit on the website. Please note there were no major changes in it, but rather making it more detailed as asked by players.
The rule states now:
c) Using More Than Two Game Clients to Play
Playing on the same game world with more than two characters. That being said, it is perfectly legal to use more than one game client to play on each world simultaneously
with up to two characters (different accounts) on each world, but only under circumstances of using second character to: make runes, train skills, hunt monsters,
refill supplies or generally move or stand in a way that doesn't prevent other players to pass through and is not interrupting other players in any other way (blocking path,
blocking access to or from deposit, blocking spawns, making traps, etc. is prohibited).
Abusing multi client by hunting monsters on the same spot using both characters (sharing experience points, blocking monsters, healing using a multi client, etc.)
or making a quest on both characters at the same time is strictly forbidden.
Punishment: Banishment or deletion depending on the severity of the violation.