RSS2.0 <category> tags are not parsed properly.

My goal: When a new feed item is added as a node, automatically assign taxonomy based on what is in the feed item.
How I think I am going to achieve it: If the feed item contains tags, use that to find proper terms in my taxonomy tables and assign those to the added node.
The problem: The tags are parsed as the string "Array" instead of the actual content.

When using this RSS feed:

<?xml version="1.0" ?>
<rss version="2.0">
<channel>
    <title>FEED TITLE</title>
    <link>http://www.example.com</link>
    <description>FEED DESCRIPTION</description>

    <item>
        <title>ITEM TITLE</title>
        <description><![CDATA[ITEM DESCRIPTION]]></description>
        <category domain="taxonomy/category">General Programming</category>
        <category domain="taxonomy/category">PHP</category>
        <pubDate>Tue, 15 Apr 2008 16:00:50 EDT</pubDate>
        <guid>8525697573E188525004F5C38</guid>
    </item>
</channel>
</rss>

The parsed source returned by _parser_common_syndication_RSS20_parse() contains wrong information. Pay attention to the "tags" entry:

stdClass Object
(
    [title] => FEED TITLE
    [description] => FEED DESCRIPTION
    [options] => stdClass Object
        (
            [link] => http://www.example.com
        )

    [items] => Array
        (
            [0] => stdClass Object
                (
                    [title] => ITEM TITLE
                    [description] => ITEM DESCRIPTION
                    [options] => stdClass Object
                        (
                            [original_author] => FEED TITLE
                            [timestamp] => 1208289650
                            [original_url] => 
                            [guid] => 8525697573E188525004F5C38
                            [tags] => Array
                        )

                )

        )

)

This is caused by this line of code:
$additional_taxonomies['RSS Categories'] = (string)explode('/', $news['category']);

I do not know why it is trying to explode it using "/", I have not had the chance to review the whole source code yet.

But I know that this will ALWAYS return the string "Array" because explode() returns an array and it is casting it as a string. An array casted as a string returns "Array" for me.

print (string)Array("hi")."\n"; <---- "Array\n"

Does anyone happen to knows what the "tags" entry of the parsed source was supposed to contain and what it was used for?

Let me know if this is not clear or if you have any questions.