RSS from WP in iframe on other sites

I’m trying to make a badge (copy and paste code – html/css only) that users can add to their site (WP.com, Blogspot, Myspace, whatever) that will display an RSS feed from a WP 2.5 blog inside a badge similar to the SpringWidgets, which are embedded Flash objects, I believe. I have a few examples at https://timbury.org/ that are working which load all the code into the sidebar. The one example which is broken is where I try to load a separate php file into an iframe. As you can see, I get the message: “Fatal error: Call to undefined function do_action() in /var/www/timbury.org/wp-includes/rss.php on line 18”

This call is working on the same page in the other 3 examples. For some reason, the code in the iframe executes in a different namespace? The environment isn’t the same. What am I doing wrong?

Then, if this can be made to work, the next step is moving the file called from the iframe to the remote server.

I don’t know if I’ve succeeded in communicating what I’m trying to do.

The code that works is this:

<!-- AnthillWidget v0.1 | WordPress | summary | Author: timbury -->
<?php include_once(ABSPATH . WPINC . '/rss.php');
$rss = fetch_rss('https://www.cre8buzz.com/anthill/?feed=rss2');
$maxitems = 5;
$items = array_slice($rss->items, 0, $maxitems);
?>
<div id="AnthillWidget" style="font:12px arial;width:250px;border:#507AA5 solid 5px;color:#999;background:#fff url(https://timbury.net/anthill_feed_header.gif) top center no-repeat; padding-top:50px;text-decoration:none;">
<ul style="border-top:#999 solid 1px;border-bottom:#999 solid 1px;">
<?php if (empty($items)) echo '<li>No items</li>';
else
foreach ( $items as $item ) : ?>
<li><a style="color:#507AA5;text-decoration:underline;" href='<?php echo $item['link']; ?>'
title='<?php echo $item['title']; ?>'>
<?php echo $item['title']; ?>
</a><br /><?php echo $item['description']; ?></li>
<?php endforeach; ?>
</ul><br />&nbsp;&copy;2008 cre8Buzz
</div>

The code pair that fails is this in the sidebar:

<!-- AnthillWidget v0.1 | WordPress | summary | Author: timbury -->
<div id="AnthillWidget" style="font:12px arial;width:250px;border:#507AA5 solid 5px;color:#999;background:#fff url(https://timbury.net/anthill_feed_header.gif) top center no-repeat; padding-top:50px;text-decoration:none;">
<center><iframe align=center width=230 height=250 scrolling=auto src="<?php bloginfo('stylesheet_directory'); ?>/iframe.php"></iframe>
</div>

And this in iframe.php:

<?php include_once('/var/www/timbury.org/wp-includes/rss.php');
$rss = fetch_rss('https://www.cre8buzz.com/anthill/?feed=rss2');
$maxitems = 5;
$items = array_slice($rss->items, 0, $maxitems);
?>

<ul style="border-top:#999 solid 1px;border-bottom:#999 solid 1px;">
<?php if (empty($items)) echo '<li>No items</li>'; else foreach ( $items as $item ) : ?>
<li><a style="color:#507AA5;text-decoration:underline;" href='<?php echo $item['link']; ?>'
title='<?php echo $item['title']; ?>'>
<?php echo $item['title']; ?>
</a><br /><?php echo $item['description']; ?></li>
<?php endforeach; ?>
</ul><br />&nbsp;&copy;2008 cre8Buzz

I’ve been banging my head for two days, any help is greatly appreciated.