Lua 5.0 was released on 11 Apr 2003. Its main new features were collaborative multithreading via Lua coroutines, full lexical scoping instead of upvalues, and metatables instead of tags and tag methods. Lua 5.0 also introduces booleans, proper tail calls, and weak tables. Other features are better support for packages, new API for loading Lua chunks, new error handling protocol, better error messages, and much more. Lua 5.0 was the first version to be released under the new (MIT) license.