I just tested this with fw 5.9.2.0.1, a USB OTG "Y" connector (injects power to device) with a keyboard plugged in, and by SSH over wifi, "evtest /dev/input/event2" generates keyboard events. This is exciting for me because I'd like to use the kindle as a writing device.
I don't see the required (i think) "keybdev.ko" in the zip (see
http://www.linux-usb.org/USB-guide/x194.html ) so not sure if that's built into the kernel or what.