Why is Firefox 2 called Bon Echo instead of Firefox?

Becaus pkgsrc makes modifications to firefox to enable it to build and
work correctly, and the Mozilla Foundation has non-Free trademark rules:

  http://www.mozilla.org/foundation/trademarks/
  http://en.wikipedia.org/wiki/Mozilla_Firefox_2.0#Trademark_and_logo_issues

You can put

PKG_OPTIONS.gecko=		official-mozilla-branding

in mk.conf and build your own packages, which Mozilla says that you
can't distribute.  See /usr/pkgsrc/www/seamonkey/options.mk for how this
gets set.