Make sure you install 10.4 build support when installing the OS X Developer tools.
MacPorts: No need for gmake from macports, as 10.6 has a recent version now.
MacPorts: I installed libsdl-devel, but I'm unsure if it's needed, haven't tried the build with it removed.
If you don't have Rosetta installed (no longer a default on 10.6), you need my patch 12014 above, as the prebuilt flex in darwin-x86 is ppc only. That was the final piece for me once I pulled Kenny Root's two patches.