A PyCLIPS user reports that the module also works on Mac OS X (darwin). I don't know much about this platform, so the only thing I can do for now is to say what he did to get it working.
Brad reports that, just changing line 984 in setup.py so that it reads
elif sys.platform[:5] in ['linux', 'sunos', 'posix', 'cygwi', 'darwi']:
and extracting the Macintosh CLIPS source code (distributed as clipssrc.sit, maybe with a different distribution of capital letters) in the clipssrc directory - probably setup.py also modifies the setup.h file in this case - the compilation and installation ends successfully.
I downloaded the Macintosh CLIPS source code, and noticed that there are files with different extensions than .c and .h: unfortunately I do not know whether or not successful compilation depends on these. Of course any feedback is welcome (and Brad, if you are tuned, drop me a line and I'll ask you some other questions... poor you!).