This repo is dedicated to add-ons which are not relying to Nightingale build system, it will contains add-ons from http://publicsvn.songbirdnest.com/client/extensions/ for example
If you are looking for downloads go here: http://addons.getnightingale.com/
You can use the script make.py to generate xpi files like this:
python make.py <add-on_folder>(add-on_folder without trailing slash)