In the WordPress.org forums, doubleedesign says:

I want to add the authors’ biographies to the end of each post.

Awesome… it’s pretty simple to do. Conceptually, what we need to do is load our co-authors, and then loop through printing the relevant information for each one.

You’ll want to put the following code snippet within The Loop in any template you’d like the bios to appear.

/**
 * Show multiple Co-Author biography fields at the bottom of a single post 
 * This snippet should be placed within The Loop
 */
if ( class_exists( 'coauthors_plus' ) ) {
	// Get the Co-Authors for the post
	$co_authors = get_coauthors();
	// For each Co-Author, echo a wrapper div, their name, and their bio if they have one
	foreach ( $co_authors as $key => $co_author ) {
		$co_author_classes = array(
			'co-author-wrap',
			'co-author-number-' . ( $key + 1 ),
		);
		echo '<div class="' . implode( ' ', $co_author_classes ) . '">';
		echo '<h4 class="co-author-display-name">' . $co_author->display_name . '</h4>';
		// Only print the description if the description exists
		if ( $description = get_the_author_meta( 'description', $co_author->ID ) )
			echo '<p class="co-author-bio">' . $description . '</p>';
		echo '</div>';
	}
}

If you’d like other co-author details to appear as well, like their avatar for instance, you can modify the output within the foreach loop.

In the WordPress.org forums, razorfrog asks:

Short of editing core WordPress code, is it possible to display the multiple authors in the site’s RSS feed?

Of course there is! From the source code, we know the RSS feed template uses the_author() to display the post’s byline information. Furthermore, the_author() echoes get_the_author() which is a filterable function. Filters allow us to programmatically change values used in a function. What we need to do is write a short snippet to produce the co-authors byline when an RSS feed is requested and Co-Authors Plus is activated.

The snippet is as follows, and can be placed in your theme’s functions.php file or a standalone MU plugin.

/**
 * Co-authors in RSS and other feeds
 * /wp-includes/feed-rss2.php uses the_author(), so we selectively filter the_author value
 */
function db_coauthors_in_rss( $the_author ) {

if ( !is_feed() || !function_exists( 'coauthors' ) )
   return $the_author;

return coauthors( null, null, null, null, false );
}
add_filter( 'the_author', 'db_coauthors_in_rss' );