Dear Pat. It seems it is its own thing; i.e. less an old something disguised as a new something and more a really new something.
From wikipedia:
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Podcasting is a way of publishing sound files to the Internet, allowing users to subscribe to a feed and receive new audio files automatically. Podcasting is distinct from other types of audio content delivery because it uses the RSS protocol. This technique has enabled many producers to create self-published, syndicated radio shows.
Users subscribe to podcasts using "podcatching" software (also called "aggregator" software) which periodically checks for and downloads new content. It can then sync the content to the user's portable music player, hence the portmanteau of Apple's "iPod" and "broadcasting". Podcasting does not require an iPod, however; any digital audio player or computer with the appropriate software can play podcasts.