Released versions can be downloaded from https://addons.mozilla.org/firefox/addon/tab-badge/
To get a working version of this repo in your Firefox profile, clone it into your extensions directory as badge@darktrojan.net and start Firefox.
cd [your profile dir]/extensions
git clone git://github.com/darktrojan/badge.git badge@darktrojan.net
Send me a pull request, or try my new experiment in add-on localization, Zoo: http://zoo.darktrojan.net/darktrojan/badge/repo.php