Running the makefile on my Mac OS 10.5 gives me (among other things):
compiling Fortran sources
Fortran f77 compiler: /usr/bin/g95 -ffixed-form -fno-second-underscore -O
Fortran f90 compiler: /usr/bin/g95 -fno-second-underscore -O
Fortran fix compiler: /usr/bin/g95 -ffixed-form -fno-second-underscore -O
compile options: '-I/var/folders/ie/ie3Fq1qC2RaKbE+BYnW87U+++TM/-Tmp-/tmp024OtW/src.macosx-10.3-fat-2.5 -I/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/numpy-1.3.0-py2.5-macosx-10.3-fat.egg/numpy/core/include -I/Library/Frameworks/Python.framework/Versions/2.5/include/python2.5 -c'
g95:f90: spectralfit.f90
/usr/bin/g95 -shared -shared /var/folders/ie/ie3Fq1qC2RaKbE+BYnW87U+++TM/-Tmp-/tmp024OtW/var/folders/ie/ie3Fq1qC2RaKbE+BYnW87U+++TM/-Tmp-/tmp024OtW/src.macosx-10.3-fat-2.5/spectralfitmodule.o /var/folders/ie/ie3Fq1qC2RaKbE+BYnW87U+++TM/-Tmp-/tmp024OtW/var/folders/ie/ie3Fq1qC2RaKbE+BYnW87U+++TM/-Tmp-/tmp024OtW/src.macosx-10.3-fat-2.5/fortranobject.o /var/folders/ie/ie3Fq1qC2RaKbE+BYnW87U+++TM/-Tmp-/tmp024OtW/spectralfit.o calc_freq_code.o dqed.o -lblas -llapack -o ./spectralfit.so
g95: unrecognized option '-shared'
g95: unrecognized option '-shared'
Undefined symbols:
"_PyModule_GetDict", referenced from:
_initspectralfit in spectralfitmodule.o
etc. etc.

I think it may be related to
http://mail.scipy.org/pipermail/numpy-discussion/2007-June/028174.html
http://mail.scipy.org/pipermail/scipy-user/2008-January/015300.html

I'll try switching to Gfortran