This script (User:Siddhartha Ghai/TWG.js) is, as of April 2012, an ongoing personal project to make a easily i18n-able Twinkle. The objective is to separate the Twinkle code from the UI messages in order to make creating modules easier.
The i18n-able code is kept in User:Siddhartha Ghai/TWG-i18n.js and modules can be created using the notes given in the comments there.
As of 3 April, 2012; this is under active development.
TWG may be loaded by placing the following in your common.js:
mw.loader.using( ['mediawiki.util','jquery.ui.dialog','jquery.tipsy'], function(){
mw.loader.load('//en.wikipedia.org/w/index.php?title=Mediawiki:Gadget-morebits.js&action=raw&ctype=text/javascript');
mw.loader.load('//en.wikipedia.org/w/index.php?title=Mediawiki:Gadget-morebits.css&action=raw&ctype=text/css', 'text/css');
mw.loader.load('//en.wikipedia.org/w/index.php?title=User:Siddhartha_Ghai/TWG-i18n.js&action=raw&ctype=text/javascript');
});