There’s another development version of XML_Feed_Parser up on the dev server. I’ve added support for atom:source and revised atom:author to work with that as per the spec, included the last few parts of core RSS2 support, added full support to the RSS1 module for the syndication and content modules, and partial support for the Dublin Core module.
I have yet to see any examples of RSS1 feeds using dc:type, dc:format, dc:identifier, dc:source, dc:language, dc:relation, or dc:coverage. If there’s sufficient demand I’ll add native support for them, but they’re not a critical concern at present.
It seems that the best way to support “official” extensions to the various feed formats is to roll them into the main classes, but I’m hoping to also add in a fallback option that will allow users to access the underlying models and retrieve simplexml objects representing elements that the package may not support. That seems to be the best way to allow for further extensibility at this point.