I love seeing new Haskell projects, though I personally would rather just stick with Haskell's clean syntax:

  data Maybe a = Nothing | Just a

...over this:

  data Maybe<a> {
    Nothing,
    Just(value: a)
  }

I understand that programmers coming from mainstream languages might feel uncomfortable without all those angle brackets, curly braces, and parentheses (why do C-like languages have so many ways to syntactically group things?), so if this project helps them ease their way into Haskell I totally support it. However, a small part of the joy of Haskell is freeing yourself from the arbitrary syntactic boilerplate that most languages have.