DHCP (rfc2131) doesn't really talk about IP exhaustion.

It's undefined behavior, and there's a bunch of people in here saying that server's have every right to violate DHCP leases, otherwise someone can take over a network by continually claiming all of a Class C by continually making DHCP requests.

That argument makes sense, but it goes very strongly against the grain of what I would think a DHCP lease meant, whcih is that it's a contract for a specific amount of time. If it is indeed a contract for a specific amount of time, the client has every right to claim what they're contractually obliged to. This was my initial assumption, and I believe it's Apple's rather valid assumption.

It's not a case of Apple not following the protocol. It's a case of the real world being more complex than the protocol.

Look at parts 3.1, 3.2, 4.4 and Fig. 5 of the DHCP protocol. They describe what a client must do on initialization. For example, section 3.2 describes what a client should do if they have a previously assigned addressed they would like to keep using. It seems to me the behavior here is very precisely defined.

Maybe a networking expert can correct me but it seems to me that those initial ARP requests before the DHCP request are not exactly in accordance with the protocol.