Wouldn't that mean reprogramming the entire game?
No, of course not. Exactly how much work the porting will be depends on the game and how it was coded, but assuming the game has been made with portability in mind (which is a fair guess, I think, since there's a Mac OS X version coming), OS specific code will be abstracted away so most of the game doesn't have to worry about it.
A real port would be possible too. But I'm not really convinced that there's a large enough Linux indie game audience out there to make the work worthwhile yet...
This is true in a way, since there's simply not that many indie games for Linux in the first place. People can't buy what doesn't exist. Meanwhile, developers are wary of porting exactly because you are -- there's not a lot of statistics available, and there's a lot of prejudice about linux users being cheap bastards (mostly because of that vocal minority I mentioned in my previous post), so they generally don't risk it. It's a catch 22.
Some have ported their classic and casual clones to Linux and seen disappointing sales -- but this is no great mystery, there's a LOT of open source competition for that kind of games. You also have to consider your target audience. There's not many middle-aged moms using Linux, for example. They do exist, in fact (much like Windows and Mac OS X, there's not just
one type of people using Linux), but if your game solely appeals to this group, you're obviously not going to see a lot of Linux sales.
On the other hand, original, high quality games sells. I personally believe that your game would fare well on Linux, simply because what you've got here looks like a high quality, original game! See, Linux users are people, too

. Many of us like good games.
Here's some posts from the indiegamer forums you can read:
http://forums.indiegamer.com/showpost.php?p=91345&postcount=21http://forums.indiegamer.com/showpost.php?p=91147&postcount=8http://forums.indiegamer.com/showpost.php?p=113393&postcount=1Also this:
http://www.gameproducer.net/2006/04/06/sales-stats-tribal-trouble/(Different genres, but at least it shows that some games can be successful.)
Also, if you do decide to give Linux a go and would like some help or guidance with your port, I'm at your service. I've got a bit of experience porting and getting things to run at various distros.