You can make your kindle registered (all things work except browser)
Use usbnetwork, and add file named "reginfo" to "/var/local/java/prefs" directory.
Structure of reginfo file:
<?xml version="1.0" encoding="UTF-8"?>
<response>
<user_device_name>Name of you kindle</user_device_name>
<global_device_name>NOT_USED</global_device_name>
<given_name>Your name</given_name>
<name>Your full name</name>
<alias>email (without @xxxx part)</alias>
</response>
P.S. If you don't have usbnetwork experience - fill this file structure with your data, and I will make update file for you.