You can use the template tag the_syndication_source_link() to display the URL of the human-readable homepage for the source that a syndicated post was syndicated from. This is exactly equivalent to outputting the value returned by get_syndication_source_link().

Sample

<?php if (is_syndicated()) : ?>
  <p class="byline">This is a syndicated post which originally appeared at
  <a href="<?php the_syndication_source_link() ?>">
  <?php the_syndication_source(); ?></a> on
  <a href="<?php the_syndication_permalink(); ?>">
  <?php the_date('j F Y H:i:s'); ?></a>
  </p>
<?php endif; ?>