ARS Technica reports Microsoft has come to it senses and has relaxed the Office 2013 EULA to allow users to move the program to a new PC. Under the original license terms, you couldn't install a retail copy of Office on a new PC, even if you removed it from the old one. The new terms allow one transfer every day unless transfers are due to hardware failures, in that case they can be made immediately.
But after much public outcry, Microsoft has relented. The Office 2013 terms and conditions are being updated so that transfers are allowed. You'll be allowed one transfer every 90 days unless the transfers are due to hardware failures. (In that case they can be made immediately.)
The change is effective immediately, but it will take some time before it trickles out to the activation servers. If you're transferring Office 2013 to a different PC and activation fails, you'll have to call customer support. Microsoft insists that the support people know the score and will be able to activate you manually.