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KS: While the developer's page says:
Mac OSX Intel CPU and “Leopard” 10.5 or later
Ubuntu 10.10 or later

... the GOG page says:
Mac OS X (10.7.0 or newer) and Linux (Ubuntu 14.04, Mint 17)

Why is that? Why can't I play the GOG version on OS X 10.6?
You can but we don't support Mac OS X 10.6 so it's a case of caveat emptor at this point :)