Add category tags for multiple terms

I was looking to do the same thing - split out multiple terms into separate category tags. Thanks for the patch - I've tested it and it works.

Will this work with D7? Has anybody tested this with D7?

Thanks for the reply batje. The feeds_tamper module was my first option but it doesn't do what I want. A field <category>category1, category2</category> will result in a category category1,category2. I used feeds_tamper's explode but to no avail.
I have looked at the patch for the D6 version and will try to change that for D7 a little later. I'll will post here once that is done. In the mean time if anybody has additional suggestions I'll try them as well.

@batje, thanks again for responding. I ended up modifying function theme_views_rss_fields_element in views_rss_views_fields.theme.inc with your D6 logic and that did the trick. On line 112 it says:

else {
  return "<$key>" . check_plain(htmlspecialchars_decode($value['#markup'])) . "</$key>";
}

I changed that to:

else {
  if ($key == 'category') { 
    $row_temp = '';
    if (strpos($value['#markup'], ',')) {
      $categories = explode(',', $value['#markup']);
        foreach ($categories as $category) {
          $category = trim($category);
          $row_temp .= "<category>".check_plain(htmlspecialchars_decode($category))."</category>";
         }
       return $row_temp;
     } 
  }
  return "<$key>" . check_plain(htmlspecialchars_decode($value['#markup'])) . "</$key>";
}

I have never done a patch so I hope people looking for a Drupal7 fix can use this solution.

Support for multiple categories added to most recent 6.x-1.x-dev version (from 2011-Nov-09). D7 version to follow.

Also, added first draft of module how-to - please read for what it can and can't do.