Line 317 sets the Auto Tweet as the Author's Website Oxtc.com - which is now a GoDaddy placeholder.
* Auto-tweet provider URL.
var $wptbsrv = 'http://wptbsrv.0xtc.com/a/';
var $settingsuri = 'options-general.php?page=wp-tweet-button.php';
Therefore, we must conclude, the plugin ran up the bill of the author. Hopefully, he has not stolen our Twitter Passwords and run.