I've been looking for something like this forever! I loved AutoIt v3 on Windows, and osascript always felt super crippled in comparison (as well as impossible to look up documentation for). I've long since forgotten what I wanted to use this for, but I'll be sure to remember this for later!
AutoHotkey is available and open source but the custom scripting language is off-putting, I would much rather have something like standard JavaScript for it. If this project moves forward in that direction it could be great.
I grew up on AutoHotkey but yeah, the syntax is very strange. It's actually based on AutoIt v2. The closest language (syntax wise) is Assembly, and that's silly.
AutoHotkey is avalible, but only on Windows. I don't think I would have made this if AutoHotkey was cross platform.