Well, actually, there are two ways to get it for free that I'm almost certain are legal, but they can be a bit of hassle and I don't know if you're up to either.
1) http://developer.apple.com/ Alright, so, get an account here (it's free), and you'll be able to download kinky stuff, but it'll be quite a hassle to install them. Still, Panther is one of the things you can download, as well as the Software Developer's Kit and lots of other cool stuff. I learned about this from my brother's friend who's a Mac genius (I mean, he builds Macs, including some out of milk cartons, and he's only like 18).
2) Hehe, this one doesn't apply everywhere, and is not a recommended solution, but if you're really desperate...If something goes wrong with your Mac, when you send it into repairs they'll put Panther on it (MAYBE they will, but maybe the won't. I don't know if everyone does it or just the store where my dad sends his iBook for repairs). Of course, if you don't have a warranty, it'll cost ya.
But, since Tiger will come out early next year, perhaps you should wait? I don't know, it's up to you. And also, you may be able to download Panther off a file-sharing program like BitTorrent or Poisoned, but I wouldn't recommend it. I mean, it's an operating system, and that's a pretty delicate matter.
P.S. It's Panther, not Pather. Just wanna point that out.
P.P.S. I think this topic is in the wrong forum. This really has nothing to do with hardware, so I'd recommend having it in the "OS X--Operating System" forum.