There was a saying about Appium (being) for apps. That still the case? Just saying since Appium is targeted towards mobile testing in general.
But there was 2 interesting posts in the old discussion forum (https://groups.google.com/forum/#!forum/appium-discuss) titled:
"Mac GUI Automation in the Appium project or someone else"
"Appium for Mac Apps - Give it a try"
if you searched for them there.
Just wanted to say, I based my work on some WebDriver interfaces to desktop UI automation tool off of the old Appium Python implementation:
https://github.com/daluu/AutoItDriverServer6
https://github.com/daluu/AutoPyDriverServer4
so you can kind of say there's an Appium for Mac and Windows Apps. 