I was having the same problem on my Mac. I'd unzipped the download and was clicking on the game, but it still wouldn't open even after checking that everything was up to date and all the permissions were good. However, I found a work around!
So, you have to:
1. Right-click the application (the actual game icon that you would normally click to play it).
2. Click "Show Package Contents."
3. Open the Contents folder.
4. Open the MacOS folder.
5. Open the Unix Executable file (icon is a black rectangle with "exec" in green) in your terminal (aka just click on it).
6. The terminal will pop up with some text on it. All you have to do is hit the enter key, and the game should start normally!
Hopefully this helps!