I compiled amule (2.1.0) to run amuled and amuleweb on a smaal homeserver, vereything works quite fine (Amule rules!), but I did indeed notice the heavy CPU usage in the frist, say, 24 hrs (average 50 to 60%, on a PII, not really a problem btw, as AMule is the main purpose of that box). Now my connection to the KAd network apparently died, and I observe that the CPU usage has dropped to average 15%.
So I see two possiblities: either the CPU has dropped because in the beginning Amule has to hash lots of files, and now it's done with that; OR indeed, like suggested, apparently KAD takes quite some CPU.
When I have fixe my KAD issue I can check wether the CPU has gone up again...