License for grammar

Hi all! I implemented Haskell grammar for ANTLRv4 based on HaskellReport 2010 and GHC source (Parser.y and Lexer.x files). Link: https://github.com/antlr/grammars-v4/blob/master/haskell/Haskell.g4 Could someone please help me figuring out which license this grammar should be published on?