Cannot Echo $username in default.php - Help!

Hi guys, I need some help!

I've added some javascript to default.php template file to customize the URL sent to addthis.com by appending the users profile URL. I need to determine $user->username from within default.php, or otherwise learn how to echo the username in this file.

I've followed the Establishing $user tutorial at AllMySocials without any luck so far, and the timeframe I have to work to isn't going to allow me to learn how to construct a CB plugin in order to pull in a single field.

I could really use some assistance getting this working and hope that I'm missing something simple!

Thanks!