I can’t create an OSX app for various reasons, but one of my testers has confirmed that the game works in modern browsers under the right conditions.
As such, Mac OSX users can play it simply by downloading the Linux version and extracting it. Then, drag /data/files/index.html into your browser window.
Two things you should know: First, you should run the game in Chrome or Firefox. (Safari doesn’t support Twine’s save system by default and there may be a few other compatibility issues)
Second, trying to play the game in full-screen will likely give you trouble, so it's best to keep it in a regular window.