The McStas code is available at GitHub:
git clone https://github.com/McStasMcXtrace/McCode
Read access is public, pull requests are accepted after review.
The top level folders and base files at this point are listed below. Those in bold are relevant to the McStas part of the tree
'''BUILD_DEPS.TXT''' - lists dependencies for building McStas (and McXtrace)
'''CHANGES_McStas''' - summery of CHANGES in McStas with every release through the project
CHANGES_McXtrace
'''COPYING''' - GPL licensing
README - General README doc
'''build_debs_mcstas''' - deb packages
build_debs_mcxtrace
'''build_macos_Lion_mcstas''' - OS X Lion
build_macos_Lion_mcxtrace
'''build_macos_Maverics_mcstas''' - OS X Maverics
build_macos_Maverics_mcxtrace
'''build_macos_Mountain_Lion_mcstas''' - OS X Mountain Lion
build_macos_Mountain_Lion_mcxtrace
'''build_macos_SnowLeopard_mcstas''' - OS X Snow Leopard
'''build_macos_Yosemite_mcstas''' - OS X Yosemite
build_macos_Yosemite_mcxtrace
'''build_rpms_mcstas''' - rpm packages
build_rpms_mcxtrace
'''build_src_bin_mcstas''' - src and bin tgz packages
build_src_bin_mcxtrace
'''build_windows_mcstas''' - Win32 build (from Linux with mingw compiler)
build_windows_mcxtrace
'''cmake''' - CMake package configuration
'''common''' - Common "library" files for McStas and McXtrace
'''doc''' - Doc folder tree
'''install-sh''' - BSD style install-sh script
'''mcstas''' - McStas code generator etc.
'''mcstas-comps''' - McStas components
mcxtrace
mcxtrace-comps
'''meta-pkgs''' - Infrastructure for meta-packages (install bundles etc.)
'''mkdist''' - Main CMake control script
'''mkinstalldirs''' - BSD style mkinstalldirs script
'''support''' - Various support packages such as Tk, CodeText perl-PGPLOT etc
'''tools''' - Perl and Python "tool layer" folder