Don't hack core files.
Additionally, the RSS feed does not offer the content flexibility of JSON.
Instead do this simple thing.
Grab the JSON output that K2 provides, process it in a standalone PHP file, outside of Joomla, and simply produce a new RSS or Atom feed. Then use this "bridge" file's feed output to to serve the feed to your third party app.
Reading the JSON file is a piece of cake with file_get_contents and then json_decode. You'll get an object which you can then transform to whatever you like. Which do you think is easier? This option or hacking the RSS/Atom driver in Joomla?
Fotis / JoomlaWorks Support Team
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