Change default Scald legend or caption output
It seems that you can alter the settings of players as much as you like, but it won't change the caption text because the pattern is hardcoded in the function theme_sdl_editor_legend() of the Scald module.

So we need to overwrite the output by something of our choice.

The previously mentioned theme function can be overwritten in your themes functions.php. Probably you use a Drupal Core or contributed theme as administrative theme, those template.php files you should not change. Thus the preferred method is below (a custom module).

Below you find a simple example of how to get rid of the "by" part in a custom module.
Effectively we just completely overwrite the output of theme_sdl_editor_legend() using an implementation of the hook_scald_dnd_library_item_alter() hook. You can change $item['meta']['legend'] to any string you like using data from $atom.

/**
 * Alter a scald library item.
 *
 * Implements hook_scald_dnd_library_item_alter()
 *
 * @param $atom
 *   The atom object.
 * @param $item
 *   The scald library item.
 */
function MODULE_scald_dnd_library_item_alter($atom, &amp;$item) {
  $item['meta']['legend'] = "
   &lt;div class='meta'&gt;
    &lt;!--copyright={$atom-&gt;sid}--&gt;{$atom-&gt;rendered-&gt;title}&lt;!--END copyright={$atom-&gt;sid}--&gt;
  &lt;/div&gt;
 ";
}