Does this work on OldSchool Runescape?

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Playing Runescape on multiple accounts and even at the same time is totally fine, however playing multiple accounts at the same time using software to control them all at ones is against the rules And will get you banned. Of course there are some people who do it but just be prepared to get banned.
Here is a fun video of a interview with someone who plays on 42 account at the same time: https://www.youtube.com/watch?v=q2kF-0vzfJ4