Luau
Fast, small, safe, gradually typed embeddable scripting language
...Luau is largely implemented from scratch, with the language runtime being a very heavily modified version of Lua 5.1 runtime, with a completely rewritten interpreter and other performance innovations. 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. ...