Of course...
Just change:
echo '<br />' . ($label4author != '' ? $label4author . ' ' : '') . $row->name;
with
echo '<br />' . ($label4author != '' ? $label4author . ' ' : '') . '<b>'.$row->name.'</b>';
and
echo '<br />' . ($label4author != '' ? $label4author . ' ' : '') . ($row->username ? $row->username : $row->name);
with
echo '<br />' . ($label4author != '' ? $label4author . ' ' : '') . '<b>'.($row->username ? $row->username : $row->name).'</b>';
Or if won't use <b>, you could replace
<b> with
<span class="author"> and
</b> with
</span>. And then you could define author's names style via CSS...