Toady, you can experiment with Linux porting absolutely for free, without mucking around with dual-booting or anything.
At www.vmware.com, download the free VMWare Server. It is a very robust piece of software that's designed to let you run more than one OS at the same time. Assuming you have enough RAM, you can easily run Linux in a window on your desktop, or run Windows on a Linux desktop.
With some hacking, you can probably even get OSX working under VMWare, but Apple takes a dim view of any such activities. The OSX86 Project is where to start looking.
You're probably going to get some static from the Linux community for not open sourcing your game. So you may find that part a bit unpleasant. However, at the same time, Dwarf Fortress is one of the best-suited games to that platform I've yet seen, both in mindset and in display mode. People that like Unix will _love_ Dwarf Fortress. And they're going to want to play it in console mode, because it's obviously 'meant' to be played that way. (even though you render it with OpenGL, which I find pretty damn amusing. )
If you can make it work in console mode (Linux terminal emulation is VERY sophisticated), that'll be preferable for most. Having it look like a terminal program but not ACT like one will unreasonably irritate some of that crowd.
I'm sure you'll make some money from a Linux port, probably more than most. On the Mac, I think you'll have a harder time of it. I definitely wouldn't spend much money on a Mac... maybe the cheapest of the Mac Minis if you don't want to do the OSX86 route.
[ September 11, 2006: Message edited by: Malor ]