RELEASED:
Kindle Paperwhite 1 is now supported as well !
I'm trying to localize PW2 to Czech and I am quite successful so far.
I took a different approach than ixtab & Co.
Instead of adding a new locale, I just 'replaced' en_GB specific files with Czech counterparts. I know that it is not POSIXly correct but it's much easier. Adding new files would be very difficult as many resources happen to dwell inside CramFS loopback files. One English locale is more than enough for a non-English speaking user anyway.
I've used Sir Alex' K3Translator to inject Czech phrases into the JARs instead of the British ones. It's very similar to K3 localization process.
To be on the safe side I don't overwrite stock files and dirs but bind-mount the Czech replacement instead. The only addition to the system is a simple upstart config file that performs the bindings listed in userstore.
An upstart config file unpacks localized files on boot, making backup when needed.
This approach should work on all Kindle models, even Kindle Touch.
I'm looking for volunteers brave enough to test the localization or able to help with translation.
When the Czech localization is ready I will be prepared to help with localizing to other languages.