> Gren started as a fork of Elm. This is mostly considered to be an implementation detail, a way to speed up initial development.
> It's not a goal of Gren to replace, or stay compatible in any way with, Elm.
A little vague but I read it as they're planning on diverging strongly and immediately with a clean break. Which doesn't make it not a fork I guess, but isn't what I normally think of when someone says a project is a fork of another.