[drakonka]

I don't mean downloading to Kindle, but actually downloading the book file to your machine where it is no longer at Amazon's mercy. If the book has DRM Calibre takes care of that, it's how many people transfer Amazon bought books to other ereaders.

[AlchemistCamp]

I'm not familiar with Calibre but AFIK, all kindle books have DRM.

[drakonka]

It is a setting the author chooses when publishing their book through KDP, and some authors choose not to enable it. Pretty sure it is enabled by default though.