The one thing I know is the license has teeth. If you exceed the license it will shut down. You bought yours so only you have ready access to your license. For example the license for 2003 has so many variations that it would be a wild guess to see what you have. Even the OEM versus retail versions differ on the install count.
So the answer is 'no', this is not the case for prior versions. We can expect the same for Office 2007.
If I need to install Office on many machines I install Open Office first then wait for someone to complain.
I heard that MS Office 2007 allows registration on up to 5 computers. Is this the case for previous versions- I have Office 2003 Small Business on my laptop and would like to download it on to my new desktop PC as well. Wondering if I can do that or if I have to buy a new version of Office (don't like the 07 version...)