I'm currently running on a MacBook Pro mid-2010 i5 with 8 GB RAM and a 256 MB VRAM video card. Operating under OS X 10.9.
I tried downloading the demo again, in case it was corrupted as you suggested. Same results, though: game hangs and shuts down. The usual window asking if I want to open the file since it was downloaded from a third party (i.e., not Apple) developer doesn't even appear.
As you stated, the .url and .html files should work fine. Guess it's an OS issue on my side. I'll see if I can solve the issue and I'll try running the app again afterwards.
Thanks for the help, though. Much appreciated.