Binos
No, it doesn't stipulate, and I've stored the two download files on the server so I could get at them again if I wanted to. I'm sure it could be burned to a CD Rom if I needed to, or loaded onto a new computer if required.
I think the standard deal with MS software is you're supposed to buy a new licence for each new installation - i.e. extra installation.
If you retire one computer and get a new one, you're only running one installation still, so you should be able to re-install the software onto that.
Once after a disc crash years ago I tried to re-install Windows XP and it told me the licence key had already been used. I rang the helpline and Microsoft reset it for me after I explained. I haven't had that happen with Office software though.
ShopArhive has live online support so if you catch them during business hours (they're in the UK) you could check the specifics. I don't think Office 2007 is available for the Mac, though. I'm an all Windows shop here, about the Mac I know very little. How does anyone survive with only one mouse button?