To build the plugin you have to install several libraries 
in /usr/local or /opt/local(via ports).

  libogg       i.e. via ports: port install libogg
  liboggz      from svn: http://svn.annodex.net/oggz/trunk
  libvorbis    i.e. via ports: port install libvorbis
  libspeex     i.e. via ports: port install speex
  libfishsound from svn: http://svn.annodex.net/libfishsound/branches/1.0-stable
  libtheora    http://theora.org
  liboggplay   from svn: http://svn.annodex.net/liboggplay/trunk

You also need the gecko sdk for your platform in /Developer/gecko-sdk:
 gecko-sdk for Intel Mac
  http://www.oxymoronical.com/site/files/gecko-sdk-mac-intel-1.8.1.3.zip
 gecko-sdk for PowerPc Mac
  http://releases.mozilla.org/pub/mozilla.org/xulrunner/releases/1.8.0.4/sdk/gecko-sdk-mac-1.8.0.4.zip