In August 2010, Jérémie Koenig published another, new version. This can be found in http://git.savannah.gnu.org/cgit/hurd/procfs.git/, branch jkoenig/master.
Testing it is as simple as this:
$ git clone git://git.savannah.gnu.org/hurd/procfs.git
$ cd procfs/
$ git checkout jkoenig/master
$ make
$ settrans -ca proc procfs --compatible
$ ls -l proc/