I often wonder why people that don't have an answer take the time to post. Really. If you don't have an answer, don't post.
That having been said...
For podpress go to line 402 or so in podpress.php and comment out the line that reads:
echo '<div id="podPress_footer" style="display: '.$diplay.'; text-align: center;"><cite>'.__('Podcast Powered by ', 'podpress').'<a href="http://www.mightyseek.com/podpress/" title="podPress, '.__('the dream plugin for podcasting with WordPress', 'podpress').'"><strong>podPress (v'.PODPRESS_VERSION.')</strong></a></cite></div>';
Save and upload. Done. You can also replace it with something else as I have done at lonelyastronomer.com.
I haven't used Spam Karma so can't help with that.