Just finished looking at the code of this widget. It is pretty easy to add additional social network links to it. You only need to do a couple of things.
1. add the appropriate icons to the images directory of the widget
2. Modify the code a little (copy and paste modifying only the area needed)
In the case below, change the name ‘SSname’ and SSiCon’ to the social network you want and the name of the icon set, accordingly.