> Can anybody explain, why FreeBSD uses the official user-agent-string
> and NetBSD does not (BonEcho/2.0) ?
> 
> "Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.8.1) Gecko/20061203
> Firefox/2.0"

They received permission? (I ask ... and now I search for answer ...)

Quickly looking at FreeBSD's ports/www/firefox I see:

--enable-official-branding

I looked at their CVS history and see revision 1.112 has:

-=-=-=-=-=-=-=-
- Mozilla license team has approved the FreeBSD Gnome team to
  use official branding for firefox and thunderbird [1]
  o Add  --enable-official-branding to mozconfig
  o Install official thunderbird/firefox icon as default.xpm icon
...

References:
        http://www.mozilla.org/foundation/licensing.html [1]
        http://people.freebsd.org/~ahze/firefox_thunderbird-approved.txt 
-=-=-=-=-=-=-=-

See the second URL above.