The critical difference is that you must download run.py from https://github.com/boostorg/boost/blob/develop/tools/regression/src/run.py

http://www.boost.org/development/running_regression_tests.html has been updated to reflect this change. Note, however, that the "Advanced use" section has not yet been changed and getting the sources from a Tarball is still not working.

Other than using the new version of run.py, existing setups do not have to change. For now, use "--tag=trunk" (the default) for develop, and to test master use "--tag=branches/release".