Unreal Tournament 2004 for Mac SNs:

47RD9-AA6PW-AM7UN-7KM4H (G5)
DEV2K-DEV46-DEV78-TJ74H (bad?)
K6T1V-M28ZP-DEV69-8JGY3 (G4)
2467K-43287-69437-TJ74H
3333H-44444-55555-BKVA9
62KYT-D3EAX-A2AVE-D76GR
NE87K-BEWWT-CE263-TJ74H
DAMNN-EYCHE-CKSUX-888XL
6969B-THNKS-34267-DZ268

Z4CH6-A76HU-A3YKE-Z2TCA (macbook, authentic)

The UT keyserver runs on port 28902, block this port on your router for outgoing traffic to prevent UT from verifying its license key online.  it will attempt to verify it when you select to Join a game.  With this port blocked, the "Internet" tab of the Join window will be dimmed.  To join an internet game, click on the "Internet" tab and then cmd-click in the empty window to pull up a contextual menu, and select "Join IP".

Note that every machine that joins a LAN game will attempt to turn in a complete list of keys in use by all machines on your LAN.  So if you block only some of the machines' access to port 28902, the others will still turn in the keys from the blocked machines, and will display an invalid key error.  This error will not cause their game to quit unless the machine that turned in the keys is using an invalid key.

All those keys are burned so if you have an internet connection you will need to block that port to multiplayer on your LAN, or pull the plug on the router.  Each person on your LAN must use a different key.  I don't play online - I have a valid key but not all the ppl at my LAN parties do, so I have that port blocked at my router.

The CD key on the mac is stored inside the application itself so if you drag and drop it to another machine it will copy the key also.  You can change the key by control clicking on the UT app and select Show Package Content.  Open "System".  The key is in "cdkey".  (if you delete the key file it'll tell you that you need to reinstall, so don't delete it, just edit it)

You can use little snitch to block access to port 28902, or you can block it on your firewall, or you can enter this terminal command to establish a temporary firewall rule to block it on that machine:   sudo ipfw add 200 deny tcp from any to any 28902