Ztecdrun is a project mainly written in Python, it's free.
ZTE Modem CDRUN enabler / disabler
ZTE USB Modem CDRUN enabler / disabler
Usage: python ztecdrun.py [port] [enable/disable]
Example to disable CDRUN on /dev/ttyUSB1:
python ztecdrun.py /dev/ttyUSB1 disable
Why would you use this? Most Telstra NextG USB dongle modems appear in Linux as a CD Drive first. Using this script this behaviour can be disabled and the modem can be used again as a normal USB modem.
Please note that this is not needed for most USB dongles anymore when using Ubuntu 10.10+.