I tailored the linker command for a particular installation. If you happened to place the png-libs somewhere else, installed a different version, or failed to install them, then it will not work. Linking of the static libraries fails due to a weakness in the build system of CS. You can start with the offending linker statement that jam prints out for you, and edit that to fit your installation.
However, if you care to test an alternate solution -- which will be included in the build guide when it is updated for the next client, then you can try to issue the following command in the directory where you compile CS:
sed 's/ -framework / -Wl,-framework,/g' out/macosxx86/optimize/libs/crystalspace_staticplugins.jam >tmp.txt && cp tmp.txt out/macosxx86/optimize/libs/crystalspace_staticplugins.jamwith the obvious modification of "optimize" to "debug" if you are building with debug information.
As a test, you can then try to compile celtst_static. That displays the same linker problems as PS does. Hence, if you successfully can build that one, then you should also be able to build static PS. Note that with this solution you should *disregard* the tailored linker statements in the mac build guide. This is still a work-around, but a much cleaner one than my previous attempt.

-Trymm.