NEXT_ROOT lives again
If you are wondering how to compile stuff on 10.3 such that it's probably backwards compatible with OS X 10.2, you'll want to set the following environment up (after having installed the 10.2 SDKs, of course):
setenv NEXT_ROOT /Developer/SDKs/MacOSX10.2.8.sdk setenv MACOSX_DEPLOYMENT_TARGET 10.2
This, of course, is only useful if the whole environment you're trying to make standalone is already 10.2 compatible. The Python 2.3.0 that comes with OS X 10.3 is most definitely not. At some point, one of the MacPythonistas will probably put together a little "chrooted" environment for building 10.2 compatible --standalone'd software (but don't hold your breath).