FWIW I think the issue is more that it's closed source than that it's using ruby.
Where did you hear that Among Us was built on DragonRuby? All I can find is that it was written in C# and Unity.
I saw it on the itch website and thought it was for ruby projects, so perhaps I'm mistaken.
Re:Show HN: DragonRuby Game Toolkit
by stolen_biscuit on Wednesday April 07, 2021 @12:58AM
(#26720763)
itch.io isn't exclusive to ruby games, it hosts games made in any engine. above commenter is correct, Among Us was made in Unity https://innersloth.itch.io/among-us hit more info to see the engine details
I always love to see ruby's focus on developer productivity being spread, and if I decide to take a crack at making a game, I'll be sure to check this out.