When building on Mac OS-X, users should follow the Unix instructions, above.
The classic MacOS version (OS 9 or earlier) of the CFITSIO library can be built by (1) un binhex and unstuff cfitsio_mac.sit.hqx, (2) put CFitsioPPC.mcp in the cfitsio directory, and (3) load CFitsioPPC.mcp into CodeWarrior Pro 5 and make. This builds the CFITSIO library for PPC. There are also targets for both the test program and the speed test program.
To use the MacOS port you can add Cfitsio PPC.lib to your CodeWarrior Pro 5 project. Note that this only has been tested for the PPC and probably won't work on 68k Macs.