Both easy_install and pip prefer to follow the download_url if it is
set (last I checked).
But the general consensus is to avoid hosting on external services, as
these just add an extra source of risk and unreliability to the
system. github, sourceforge or Google code all suffer from downtimes -
far more often than you'd expect. pypi has a couple of geographically
distributed mirrors by now and pip/easy_install/buildout can use
those.
So I'd suggest we remove the download_url for the next release.
Hanno