To join a very populated “costume” game, you must wait for Halloween and send open house invites.
(I know, I’m being a smart-ass 
)
This game is made for 100 vs 100 lone wolf
It’s not his first time using this word, so we should teach him the correct one.
his other topics: Costume Skins / Sounds Like Warthunder or this Make HUD More Costumizable
So @anon85183669 the word you are looking for is “CUSTOM” like here:
because COSTUME can be like this 
But more seriously, to answer your question, servers like this are sort of ghost servers, they actually are not existing, nothing happens there. If you look closer on your screenshot you can see 2 more similar servers, they always have time set at 00:00, there is also no Creator of these rooms/custom battles.
i dont care if i write the genocidal english language badly. Have a good day nerd
Meanwhile a certain Cyrillic country which caused the Holodomor (and attempt doing it again…) eheh, sure, scrub.