Please see the answer to your question regarding your ROVL question.
The receiver and transmitter will both operate while either end is moving. The range and direction are updated once per second.
Only one transmitter can be in operation in an area at any given time, but any number of receivers can home in on it. If the range information is important and needs to be stable over long time periods, then all the receiver clocks should be calibrated to the transmitter (directions are in the user manual). If the receiver is rigidly mounted to the AUV, the receiver IMU can be ignored, and the AUV can be guided by the apparent angle outputs of the receiver.
*"I am looking for a low cost USBL that I can use for my 2 AUV models to home into a moving target underwater. I presume I need 2 sets of transmitters and receivers, one for each AUV, and one for each location on the moving target. *
The target is also moving, so can you confirm that the range and bearing can be calculated while both the transmitter and receiver are moving."