License for grammar

[Евгений Слободкин]

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?