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 188.8.131.52 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 <email@example.com> Wed, 06 Apr 2011 22:48:55 -0700
debian-policy (184.108.40.206) 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.