7kAA is legally free. Visit Wikipedia page, 7kfans.com, and of course Desura! So why are you still charging for it?
You could also compile the open patch binary for Mac to make it available there!

In fact, the free version runs on my computer, while the GOG version does not ... well, at least I only spent $1.80 or so.

I've installed the open source 7kaa on every new Linux installation; I bought the game in 1997 and loved it. an have urged Linux users to buy the GOG version to get the (nearly essential) manual.

I compare it to the Dominions series: barely serviceable graphics, and deep, deep gameplay.