Correct, Office 2008 does not require activation... You can install on multiple Macs with the same license code, if none of those Macs are on the same network.
The Home & Student version comes with 3 keys. If you have 4 Macs on the same network, you can install on all 4 if you want. But, only 3, with different license, will run Office apps at the same time while connected to the network. Office checks for other Office apps running on the same network. Same license will not work from two or more Macs. Disconnect from the network, and you could have dozens of Macs, all running with the same license. But, no network/internet which would allow the Macs to "see" the others.