“switch11” on iReader Review quotes tech pundit Andy Ihnatko in an appearance on a podcast saying that there are EPUB reader apps in development for the Kindle:
I believe now that there’s an actual app development kit for Kindle .. I have talked to a couple of people who have said that they want to build an ePub reader that would run on the Kindle. And Amazon says they don’t care – go ahead.
switch11 notes that Ihnatko may have been confused, but even if he wasn’t it is unclear whether Amazon would approve such an app as it seems to go counter to their “no generic readers” development rule. I would be inclined to agree—it doesn’t seem likely that Amazon would allow EPUBs in the back door after refusing to let them in the front. Even if it did, it’s doubtful any EPUB DRM format would be supported. I suppose we’ll have to wait and see.
The entry also mentions a couple of audiobooks apparently free to Kindle users outside the US (or who reset their country to “Canada”), as well as eight free classic Doctor Who novels (including Human Nature, turned into a 2-part 10th Doctor episode, and Lungbarrow, considered one of the 7th Doctor’s finest adventures) available for download in PDF and PRC (MobiPocket) format.