This looks reasonably interesting, and Evan is extremely thoughtful about design; I know he’s put a huge amount of work into this.

Personally, I’d be very cautious about adopting closed-source software with such a restrictive license as part of an application, especially given the context of Elm’s trajectory. When Elm went through breaking changes or regressions, or was not worked on publicly for years, users had access to the source and the right to modify it. With Acadia’s licensing, you’d be stranded.