Luau
Fast, small, safe, gradually typed embeddable scripting language
...The runtime mostly preserves Lua 5.1 API, so existing bindings should be more or less compatible with a few caveats. Luau is used by Roblox game developers to write game code, as well as by Roblox engineers to implement large parts of the user-facing application code as well as portions of the editor (Roblox Studio) as plugins. Roblox chose to open-source Luau to foster collaboration within the Roblox community as well as to allow other companies and communities to benefit from the ongoing language and runtime innovation. ...