Region X version 1.6 is available at http://xvi.rpc1.org
It's an Universal Binary and has been tested on MacOS X 10.3.0 and up. Yes, MacOS X 10.3.0 is able to run universal binaries, of course only the PowerPC part. It seems OS X has always been able to.
If you are running an older version of Mac OS X, you may try this universal version, it should work. But if you have trouble, a PowerPC-only version is also available. I'd like reports from people running it on older MacOS X (up to 10.3.x).