Fink should no longer be needed, but I don't think it will hurt. From the Xcode package, X11 must be installed, but the llvm-gcc compiler libraries are not used. I believe if the glib library is not installed with fink, it will be used from the AFNI distribution if you set DYLD_FALLBACK_LIBRARY_PATH to point to your AFNI binary path as in this thread:
The command "otool -L 3dSkullStrip" shows what 3dSkullStrip expects, and it seems one /sw library from fink is there. The FALLBACK path provides a way to get that library from another path.