The Elm project forked into a bunch of different Elms because Evan basically abandoned / killed it. Then he got more interested with this project. What’s to say that won’t happen again?
https://acadia.engineering/license/faq
The way I read this, Acadia is an attempt to finance working on both it and Elm.
- There's an outside chance you're doing Zokka to allow for custom package repos (I think that's the only difference).
- You may be using the Lamdera compiler to use Set and Dict natively with your custom types.
If you're doing something other than compile Elm to JS for UIs, you may in fact be using one of the actual forks.