Many people worked on finishing DEP 5. I think that the blog of Lars does not show enough how collective the effort was.

Looking in the specification's text, one finds:

The following alphabetical list is incomplete; please suggest missing people:
Russ Allbery, Ben Finney, Sam Hocevar, Steve Langasek, Charles Plessy, Noah
Slater, Jonas Smedegaard, Lars Wirzenius.

The Policy's changelog mentions:

  * Include the new (optional) copyright format that was drafted as
    DEP-5.  This is not yet a final version; that's expected to come in
    the 3.9.3.0 release.  Thanks to all the DEP-5 contributors and to
    Lars Wirzenius and Charles Plessy for the integration into the
    Policy package.  (Closes: #609160)

 -- Russ Allbery <rra@debian.org>  Wed, 06 Apr 2011 22:48:55 -0700

and

debian-policy (3.9.3.0) unstable; urgency=low

  [ Russ Allbery ]
  * Update the copyright format document to the version of DEP-5 from the
    DEP web site and apply additional changes from subsequent discussion
    in debian-devel and debian-project.  Revise for clarity, to add more
    examples, and to update the GFDL license versions.  Thanks, Steve
    Langasek, Charles Plessy, Justin B Rye, and Jonathan Nieder.
    (Closes: #658209, #648387)

On my side, I am very grateful to Bill Alombert for having committed the document in the Git repository, which ended the debates.