PyMOL is a very popular 3-D molecular visualization tool. It also happens to be a great bargain. PyMOL is free, as in open source.
Unfortunately, all attempts to install PyMOL on an OS X system (as per the INSTALL file) led to errors:
This appears to have something to do with more recent version of OS X build tools lacking Power PC architecture dependencies. A question on Superuser prompted me to try this solution:
$ ARCHFLAGS="-arch i386 -arch x86_64" python setup.py build
After an encouraging period where a lot seemed to be happening, the build process terminated with the same complaint from lipo.
Fortunately, there is another way. MacPorts makes it very easy to install the most recent version of PyMOL (1.4.1) and all of its dependencies with:
$ sudo port install pymol