I had the same problem (it just said "the application IntelligentDesignMac can't be opened"), but could actually fix it by going through these steps: https://discussions.apple.com/thread/7586240. Basically navigate to the app in terminal and then chmod +x it. (That guide assumes you have it in Applications, but it is easy to translate to other places)
Viewing post in Guide for MacOSX compatibility
After which command? It looks like a problem of navigation, but maybe it's something else. I did it by directly opening terminal at the folder the game came in by right-clicking the folder, then doing " cd IntelligentDesignMac ", " cd Contents/MacOS ", "chmod +x * ". That star should mean the game, since there's nothing else in the folder. Hope you can get it to work!
I typed this in my terminal but its not opening anything sadly :(
cd
cd Applications
cd /Applications/IntelligentDesignMac-2
cd /Applications/IntelligentDesignMac-2/IntelligentDesignMac.app/Contents
cd /Applications/IntelligentDesignMac-2/IntelligentDesignMac.app/Contents/MacOS
chmod +x /Applications/IntelligentDesignMac-2/IntelligentDesignMac.app/Contents/MacOS/IntelligentDesignMac
Well, you shouldn't do any of the cd commands, since you chmod the full name of the file anyway. You should just open a fresh terminal window at your user and directly do " chmod +x /Applications/IntelligentDesignMac-2/IntelligentDesignMac.app/Contents/MacOS/IntelligentDesignMac". Doing the cds is exactly what changes the navigation. Sorry if I confused you!