My port of XTerm stopped working with 5.3 firmware. Instead of trying to revive it I took another way. I wrote a very simple GTK+ terminal emulator based on VteTerminal library.
It is available for testing here
I run it successfully on KT 5.3.2 firmware. It is reported to run fine on Paperwhite. I believe it should also be compatible with 5.1 firmware.
UPDATE: It is reported to run on following devices: KT, KT2, KT3, PW1, PW2, PW3.
Any feedback welcome