Post using fake usernames?

[Cip]

I found a hack that allows users to manipulate the userid behind the post (Post by Proxy mod), but I couldn't find one that allows you to manipulate the username so that it would show up as a user that does not exist.

This is how my custom posting code looks, but it doesn't seem to matter if I manually set the $newpost['username'] to "Fake Username";

PHP Code:

            $poststarttime = $vbulletin->input->clean_gpc('p', 'poststarttime', TYPE_UINT);
            $poststarttime = time();
            $posthash = md5($poststarttime . $vbulletin->userinfo['userid'] . $vbulletin->userinfo['salt']);
            $forumid = 17;
               $foruminfo = verify_id('forum', $forumid, 0, 1);
               $threadid = 493;
               $threadinfo = verify_id('thread', $threadid, 0, 1);
            $newpost['username'] =& $vbulletin->userinfo['username'];
            $newpost['message'] = $_POST['custompagetext'];
            $newpost['title'] = $_POST['custompagetitle'];
            $newpost['parseurl'] = '1';
            $newpost['poststarttime'] = $poststarttime;
            $newpost['posthash'] = $posthash;

            if ($vbulletin->userinfo['autosubscribe'] != -1){$newpost['emailupdate'] = $vbulletin->userinfo['autosubscribe'];}
            else{$newpost['emailupdate'] = 9999;}
            if ($vbulletin->userinfo['signature'] != ''){$newpost['signature'] = '1';}
            else{$newpost['signature'] = '0';}
            $post = array();
            $post['visible'] = 1;
            $newpost['visible'] = 1;
            $threadinfo['visible'] = 1;

            build_new_post('reply', $foruminfo, $threadinfo, $post, $newpost, $errors);
        $currcont_query = $db->query_read('SELECT username, pagetext, title, dateline, postid FROM ' . TABLE_PREFIX . 'post WHERE threadid = 493 ORDER BY postid DESC LIMIT 1');
        $current = mysql_fetch_row($currcont_query);
         approve_post  ($current[4],  0, true, NULL, NULL, true);