To get source code you can use CVS, get source code of everything here or use SourceForge to get each package.

If you'll use CVS, modulename can be modulos, elf2mod, elf2emod, elf2lmod, mkext2boot or startfile.

The most recent code from CVS (not using -r or using -r HEAD after co) may not work, to get a working source code (at least with Bochs), use -r stable after co.