Thanks for adding a mac version but unfortunately it doesn't work.
It's my first time encountering such error. I've sometimes had to fiddle around with the permission rights of the app contents but nothing like this. Can you repackage and upload or even rebuild?
This looks like it's a Unity game so it should work just fine (and since it's 2d you're probably not using any weird shaders that would make it to not work)...
edit: Actually, got it working by running by manually launching it from console with:
./Only a Lab Slime.app/Contents/MacOS/Mac_Runner.
And I guess it wasn't Unity after all. I guess Unity and GameMaker both have similar looking end products with default settings such as "(c) 2017 CompanyName" etc...