Supposedly, a number of other people who were streaming Royals got suspended/banned. Twitch suspending or banning people for streaming a free game is a breach of First amendment rights.
I suppose Nexon always maintains the right to do this with material involving private servers like Royals. Why after all these years they would be bothered by any Royals content when GMS is so different (and shitty) and there is little overlap in communities is beyond me. They must think there is some lost money to be made from private servers running decade plus old versions of the game with loads of custom content. Royals to me is literally the idealized version of Maplestory without all the money grubbing p2w bullshit and people that play it likely didn't enjoy the direction GMS took the game in anyway. Sorry that happened man hope you can fight the ban somehow.
If you are a content creator on Twitch beyond streaming MapleRoyals for your friends or for fun, I highly suggest reading through the Terms of Service and particularly the Community Guidelines if you have not done so already. Keep in mind that Twitch specifically prohibits streaming "content from unauthorized private servers" which are inherently in violation of copyright laws. While Twitch has not historically bothered to stringently enforce this rule against small streamers, players have reported being banned for streaming MapleRoyals (as well as other MapleStory private servers). As far as I'm aware, Nexon has even gone through the lengths of hiring a private firm to crack down on streamers promoting private server content. While we obviously love that players are making use of streaming services to have fun and promote the old-school MapleStory experience, please be aware of the risks you face when doing so.
