Oops, assumed you'd know what I meant by "Darwin". It's actually the other way around, you know: Darwin is Apple's variant of the BSD Unix kernel, which they use as the base on which Mac OS X and iOS run, the way Gnome and KDE run on the Linux kernel. (iOS is such a walled garden that it's difficult to tell, and I wasn't thinking of it, but it is Darwin at its kernel.)

Lion post-dates Snow Leopard, so it looks like QB64 will work. Thanks!