As noted in your release notes, D:OS requires Mountain Lion or later. The Steam client does download and install D:OS on my 2006 Mac Pro, but when I try to run it, it crashes. No surprise there. My machine runs Lion and can't upgrade the OS beyond that. (There's an unsupported, tricky workaround to upgrade to Mountain Lion or later that I'm not going to use.)
QUESTION: are you sticking with this policy or is there a chance D:OS will support an earlier version of the Mac OS?
