It was unfortunately reported yesterday by a number of sources that Amazon had released the source code for the software running on the Kindle DX.
This isn’t all of the Kindle source code. It’s a selection released in order to comply with the license requirements of the code originally written by other people (like the GNU Project) which Amazon modified for its own purposes.
Code that gives them significant power over users and how we can access books (in ways that have nothing to do with actual copyright law) remains secret.