I downloaded prince-8.0-macosx.tar.gz from http://www.princexml.com/download/
Following the instruction in README.TXT, I could install prince on Mac OS X 10.7.6.

The problem is that when I try to run prince. I got this error message "DIRECTORY" is the name that prince is installed.

DIRECTORY/prince: line 3: DIRECTORY/prince: Operation not permitted
DIRECTORY/prince: line 3: DIRECTORY/prince: Undefined error: 0

What might be wrong?

This is on an Intel Mac, not a PowerPC Mac, right?

Can you try running /usr/local/lib/prince/bin/prince --version, assuming Prince was installed in /usr/local?