Kindles can read a variety of non-proprietary, non-DRM'ed formats. They read TXT, HTML, JPEG, and non-DRM Mobi files directly.
Non-DRM Mobi books, like free e-books found online in Mobi format, or files you convert to Mobi files, are already supported on Kindle.
The Kindle only allows the reading of Amazon DRM-protected content.
DRM is not to prevent other files from being readable on the Kindle.
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