The source code for released versions of Apple's GCC is available at `http://www.opensource.apple.com/darwinsource/', in `.tar.gz' format.
For unreleased versions (including 'seeds', beta versions and engineering roots), source can be obtained by asking the Apple contact from which you obtained the unreleased version.
For many versions of Apple's GCC, source code is available by using anonymous Subversion. You may obtain Subversion ('SVN') from `http://subversion.tigris.org/project_packages.html'.
Development of this version is done at `svn://gcc.gnu.org/svn/gcc/branches/apple-local-200502-branch'.
For example, you can fetch the latest version by entering:
$ svn co svn://gcc.gnu.org/svn/gcc/branches/apple-local-200502-branch
Each version will be tagged based on its build number, which you can find by executing `gcc --version'; for instance, if this prints
gcc (GCC) 3.3 20030304 (Apple Computer, Inc. build 8402)
then the build number is 8402. Some older compilers may require you use `gcc -v' to obtain the build number. Once you have the build number, its tag will be at `svn://gcc.gnu.org/svn/gcc/tags/apple', like `svn://gcc.gnu.org/svn/gcc/tags/apple/gcc-8402'. You can list all the tags by writing
$ svn ls svn://gcc.gnu.org/svn/gcc/tags/apple
Then check out a particular version by writing
$ svn co svn://gcc.gnu.org/svn/gcc/tags/apple/gcc-8402
The above command won't succeed as written, because 8402 is not yet a real compiler build number.