Not necessarily, since it's in production they might be hoping for a bit of securty-by-obscurity if they haven't had time to get an audit the code (runtimes are always hard to get 100% correct since they're so generic, esp for a language such as Lua).
Seems like this runtime was announced to Roblox developers almost a year ago. But i don't think they've put much thought or effort into open sourcing it and it just happend to pop up in peoples feeds now since Arseny published an article(#1) about his 8 years working for Roblox 2 days ago and somebody probably took the link from that article (Quite an interesting read if you're into gamedev).
Seems like this runtime was announced to Roblox developers almost a year ago. But i don't think they've put much thought or effort into open sourcing it and it just happend to pop up in peoples feeds now since Arseny published an article(#1) about his 8 years working for Roblox 2 days ago and somebody probably took the link from that article (Quite an interesting read if you're into gamedev).
#1 , https://zeux.io/2020/08/02/eight-years-at-roblox/