To start install, I had to download all 35 files from:
http://svn.automattic.com/backpress/trunk/
or
http://phpxref.ftwr.co.uk/bbpress/nav.html?bb-includes/backpress/
to bb-includes/backpress/
It then stopped nagging.
Any idea why aren’t these bb-includes/backpress/* included in https://trac.bbpress.org/browser/trunk/bb-includes ???
