By default the sources are obtained from the Boost Subversion Repository and we prefer testers use SVN. But if you can't have an SVN client installed you can obtain the sources as tarballs (*.tar.gz). To indicate this pass an empty user to run.py:
python run.py ... --user=
Note: Both methods to obtain the sources will get the latest code. This is accomplished by building the tarball on-demand from the SVN sources.
--Beman