This tool was originally posted to http://www.dudek.org/blog/180 by Gregory Dudek. The site seams to be down and the code cannot be downloaded from there anymore.
This file was downloaded from https://code.google.com/p/avr-uip/downloads/detail?name=xbee-gdxctu.py
The last entry of the blog in the internet archive can be found at https://web.archive.org/web/20111225024352/http://www.dudek.org/blog/180.