...blogger Kristan Kenney, the licence agreement included with the recently leaked version states that "if you are a 'QualifiedFamily Pack User', you may install one copy of the software marked as 'Family Pack' on three computers in your household...
http://software.silicon.com/os/0,39024651,39448349,00.htm
...details in the latest build of Windows 7 have the following clause under 'Installation and Use Rights': "If you are a 'QualifiedFamily Pack User', you may install one copy of the software marked as 'Family Pack' on three computers in your household...
http://www.itworld.com/windows/70158/windows-7-may-get-family-pack-discount