You can go either way. I myself use a multi-instance license on my fuzzers; all VMs have the same license to use BugId. You can request one by specifying the number of machines you want to be able to run it on and I'll get you a quote so we can discuss a fair price.
manual analysis of crashes from a fuzzing farm => single instance license. automatic analysis in a fuzzing farm => multi-instance license. automatic analysis from fuzzing farm on single machine => needlessly complex waste of time to save a few bucks on a multi-instance license.