Can you use DHCP leased IP addresses for Change Auditor hosts, or do you need to use statically assigned IPs? (4348950)

You can use DCHP addresses for your hosts, however, you should use "Static Reservations" so that your IP addresses don't accidentally change and cause issues.

What is important is that the IP address doesn't change and that the DNS registration is up to date in your environment.  It is also important that the subnet that you are using is assigned properly to an AD Site. 

The service connection point (SCP) that the client and agents use to locate the coordinator, should get updated with new IP and port information every time the coordinator service starts.  Assuming that the coordinator's IP doesn't change while it is operating (which shouldn't happen when you use a reservation), you should have no issues.