Seems to be GPLv3 https://github.com/chkas/easylang/blob/394e29a44458ac67f8483... although I think the line right above that stating "All rights reserved" is actually incompatible with GPLv3 which is designed to grant rights, not reserve them. I am not lawyerly enough to know what the story is with that "must contain a built-in function" clause.
Kind of sad it's not self hosted yet :-D