I reflashed a demo Kindle DXG to factory using pretty much the same technique some 7 years ago. Hardest step was soldering connectors for UART to USB bridge.

I reflashed a demo Kindle DXG to factory using pretty much the same technique some 7 years ago. Hardest step was soldering connectors for UART to USB bridge. Luckily had a friend handy with a soldering iron. After that I used a terminal program to get to uboot screen and simply upload new factory image (I think zmodem was supported). I also got SHH access to the device. I vaguely remember some sort of weird process for obtaining password. It seemed Kindle apps at the time were just a bunch of jars Most of the information came from a collection of posts on mobileread forums. At the time Kindle DX was selling for $200+ on eBay while demo(locked) versions were selling under $50 in quantities of 100. The demo Kindles were used as display models in some brick and mortar store(Best Buy?). I briefly considered starting a small venture reflashing those Kindles but then decided against it. Sony DPT-S1 came out and was so much nicer to use than Kindle.