The KOReader Autolaunch extension toggles a boot script that opens KOReader as soon as the Kindle finishes starting up. The script leaves Amazon’s UI running so the process remains stable, and you can reverse the change at any time from KUAL.
extensions/ directory on your Kindle.bash /mnt/us/KOReader-autolaunch-remove.sh inside KOReader’s terminal emulator.koreader.sh in the koreader/ folder, perform option 1, then restore the filename.