What does the “Disable Drivers” header on the RM024 DVK do and what is it used for?

The Disable Drivers jumper pins disable the RS232 drivers by creating a buffer between the RS232 and the radio. This will then allow you to pipe your own signals into the radio. If you do not disable the drivers, then you would have outputs from the buffer as well as your device. Therefore, both outputs would be trying to drive the same signal.