Preserving line breaks when saving and displaying custom fields data

I dont't know which form plugin you use and how it saves data to the database. But I would asume that the linebreaks are saved to the database.

But as you might know, a line break in the source code of a HTML page does not show a line break on the browser. The is a very handy PHP function called nl2br() which will add a
tag for each line break in the user content text.

This seems to work fine:

<? $source = get_post_meta($post->ID, '_aboutus', true);
if($source){
$source = explode("\n", $source); ?>
<? for($i = 0;$i<sizeof($source);$i++){ ?>
<? echo $source[$i]; ?><br />
<? } ?>
<? } ?>
<?php if(get_post_meta($post->ID, '_aboutus', true)):                                       echo '</div>'; endif; ?>

This could probably help,

http://codex.wordpress.org/Function_Reference/wpautop

This converts the new lines into html <br/> tags

What I like to do is re-create all the default filters that are applied to the_content by adding the following in functions.php.

/* 
 * Recreate the default filters on the_content
 * this will make it much easier to output the meta content with proper/expected formatting
*/
add_filter( 'meta_content', 'wptexturize'        );
add_filter( 'meta_content', 'convert_smilies'    );
add_filter( 'meta_content', 'convert_chars'      );
add_filter( 'meta_content', 'wpautop'            );
add_filter( 'meta_content', 'shortcode_unautop'  );
add_filter( 'meta_content', 'prepend_attachment' );

Then the template code would look like:

<?php 
if( $about = get_post_meta($post->ID, '_aboutus', true ) ): 
  echo '<div class="companyaboutus">'. apply_filters( 'meta_content', $about ) . '</div>'; 
endif; 
?>

You could, of course, use the_content but I found that plugins also like to hook into that for displaying sharing buttons and the like and so this method avoids sharing buttons from taking over your page.