I've been slumming it on a Mac OS X 10.2.8 machine lately and was disappointed to discover it appeared running Arduino on it wasn't an option. Being somewhat stubborn and somewhat of a masochist I decided to see what could be done about it.
I had seen a reference to a fix for 10.2 (I think it came from the Processing code) in the IDE source which surprised me a little but made me wonder what parts of Arduino would run on 10.2 successfully. (The FTDI driver also seemed to be 10.2 compatible.)
It turns out the 0010 IDE runs on 10.2 without any issues at all, but when you try to compile anything it fails.
Long story short, it turns out that avr-gcc 4.x and other tools as compiled aren't compatible with 10.2 and in fact it seems avr-gcc 4.x can't be compiled for 10.2 at all. (Or at least no one seems to have gotten it to do so.)
But, it turns out that avr-gcc 3.x can be compiled for OS X 10.2 and once it's patched to support new devices it also works for Atmega168 code compilation. Using a 3.x gcc version is apparently a valid solution because I'm told some distributions of Linux such as Gentoo only ship with 3.x and Arduino runs there. (Which does make me wonder why the Mac version ships with 4.x gcc--of note is the fact the avrdude supplied ran without modification.)
I'd be interested to hear if others had success with this.