So although the mac gcc 4.0.1 distribution aims to support OSX 10.3 there is one problem  , namely using built-in '/usr/bin/ld'.

Here is the output of compiling a simple program (all executable link phases fail with the latest bits)

/usr/local/gdc/bin/gdmd -v -v1 -g -ofcb cb_d.o cb_c.o
Using built-in specs.
Reading specs from /usr/local/gdc/bin/../lib/gcc/powerpc-apple-darwin8/4.0.1/../../../libgphobos.spec
rename spec lib to liborig
Target: powerpc-apple-darwin8
Configured with: /Users/dvdf/Data/Staging/r0.22rc2/gcc-5363/build/obj/src/configure --disable-checking -enable-werror --prefix=/usr --mandir=/share/man --enable-languages=c,c++,d --program-transform-name=/^[cg][^.-]*$/s/$/-4.0/ --with-gxx-include-dir=/include/c++/4.0.0 --with-slibdir=/usr/lib --build=i686-apple-darwin8 --program-prefix= --host=powerpc-apple-darwin8 --target=powerpc-apple-darwin8
Thread model: posix
gcc version 4.0.1 (Apple Computer, Inc. build 5363) (gdc 0.22, using dmd 1.004)
/usr/local/gdc/bin/../libexec/gcc/powerpc-apple-darwin8/4.0.1/collect2 -dynamic -arch ppc -macosx_version_min 10.3 -multiply_defined suppress -weak_reference_mismatches non-weak -o cb -lcrt1.o /usr/local/gdc/bin/../lib/gcc/powerpc-apple-darwin8/4.0.1/crt2.o /usr/local/gdc/bin/../lib/gcc/powerpc-apple-darwin8/4.0.1/crt3.o -L/usr/local/gdc/bin/../lib/gcc/powerpc-apple-darwin8/4.0.1 -L/usr/local/gdc/bin/../lib/gcc -L/usr/local/gdc/bin/../lib/gcc/powerpc-apple-darwin8/4.0.1/../../.. -L/usr/lib/gcc/.. cb_d.o cb_c.o -lgphobos -lgcc_s.10.4 -lgcc -lm -lSystemStubs -lSystem
/usr/bin/ld: unknown flag: -macosx_version_min
collect2: ld returned 1 exit status
make: *** [cb] Error 1

If I attempt to link manually by removing the macosx_version_min flag I run into a few more issues (possibly related)?

first:
/usr/bin/ld: can't locate file for: -lgcc_s.10.4

second:
/usr/bin/ld: can't locate file for: -lSystemStubs

At this point I've complete hosed the link for sure but here is the final error messages for fun:

/usr/bin/ld: /usr/local/gdc/bin/../lib/gcc/powerpc-apple-darwin8/4.0.1/../../../libgphobos.a(deh.o) malformed object (stray relocation PAIR entry (1) in section (__TEXT,__eh_frame))
/usr/bin/ld: /usr/local/gdc/bin/../lib/gcc/powerpc-apple-darwin8/4.0.1/../../../libgphobos.a(deh.o) malformed object (stray relocation PAIR entry (3) in section (__TEXT,__eh_frame))
/usr/bin/ld: /usr/local/gdc/bin/../lib/gcc/powerpc-apple-darwin8/4.0.1/../../../libgphobos.a(deh.o) malformed object (stray relocation PAIR entry (5) in section (__TEXT,__eh_frame))
/usr/bin/ld: /usr/local/gdc/bin/../lib/gcc/powerpc-apple-darwin8/4.0.1/../../../libgphobos.a(deh.o) malformed object (stray relocation PAIR entry (7) in section (__TEXT,__eh_frame))
/usr/bin/ld: /usr/local/gdc/bin/../lib/gcc/powerpc-apple-darwin8/4.0.1/../../../libgphobos.a(deh.o) malformed object (stray relocation PAIR entry (9) in section (__TEXT,__eh_frame))

I'll probably sync and do a build to try and get my own compiler running in the short term but hopefully this can be fixed in the binary dist.

I'm not sure the GCC 4.0.1 distribution supports 10.3 or earlier, I think it is for 10.4 only ?