The "redeem" button does not appear in the Podcast app on iOS 5 handsets as first noted by Cult of Mac, though the graphic is present on iDevices running the iOS 6 beta and when clicked opens a separate "Redeem" page much like the existing iOS App Store.
It should be noted that the Podcast app uses the same iTunes pipeline and storefront as the iTunes app which allows Apple to update the app sans and iOS change, possibly explaining the presence of the redeem button in iOS 6 beta. Another possibility is that redeem codes could be used by content providers in lieu of having a user search for a particular podcast, meaning that instead of adding funds to an account the redeem code could be used as a navigation tool.
What is unclear is why the redeem button appears only in the upcoming version of Apple mobile OS and not in the current iOS 5, leaving room for speculation that the company may be looking into monetizing podcasts.
The new Podcast app's redeem button and subsequent landing screen only appears on devices running iOS 6.
If Apple were to allow podcast creators to charge for their content, it would be the first such play at pay-per-download or subscription-based distribution since the digital shorts were introduced in the iTunes Store in 2005.
Thus far Apple has forbade podcasters to charge for their media in any direct way which has prompted some to seek financial backing through workarounds like in-show advertising or website donations. For example the popular Adam Carolla podcast, which hovers near the top of the iTunes charts, runs "live reads" from a variety of third-party advertisers and promotes its own partnership with Amazon that metes out a small percentage of whatever sale is made after a user "clicks through" an advertisement banner to the online retailer's site. Not only does this technique allow Amazon real-time advertising analytics, but it gives podcasters a way to make money that is beyond Apple's purview.
As podcasting continues to grow and become increasingly lucrative with big-name providers including TED Talks and NPR programming, Apple is missing out on the cottage industry it helped to create. It is possible that the iPod maker could be mulling over a royalty-based distribution model much akin to how iTunes handles music, movies and books. Whether a new pricing scheme will have an effect on downloads is also unknown, though podcasters could see equal or higher revenues under the speculated system even with a smaller audience.