Not sure if you have to use CodeGuru with BugBust, they don't clarify.
>(after the 30 day free trial of BugBust and 90 day free trial of Profiler).
So it's not free, dev time is expensive and has a lot more value than their proprietary service usage time—so they're coming out on top whilst charging people for it.
BugBust itself is free. You pay for usage as per normal for CodeGuru Reviewer and CodeGuru Profiler (after the 30 day free trial of BugBust and 90 day free trial of Profiler).