If you buy a copy of Microsoft Office 2013 you will only be able to install it on ONE machine. You will not be able to transfer it to another system, even it is lost, stolen, or damaged, Microsoft has confirmed.
This is Microsoft's way of encouraging customers to opt for the Office 365 version of the software. The subscription based model offers the ability to transfer your software on up to five machines. This does not mean you can put one copy on five machines at once. As the service is cloud based, it pings your machine to ensure that the machine you registered with it is in fact the machine you have on file.
The subscription is $9.99 a month, or $99.99 annually. So it's like buying office every year. However, you get ALL the office programs for the price. Currently to get ALL the programs you're going to be paying roughly $400 or MORE retail. So if you're using all the programs you're really only buying Office every four or so years, and that's not so bad.
Adobe rolled out with their subscription based software as well. The Adobe Creative Cloud Subscription is set up much the same way. At $50 a month you get a license to EVERY Adobe CS6 product that is available and publishing space. I'm a member and I love it.
So time will tell if these subscription based software applications will stick. The Adobe CS6 Master Collection is $2600, so that's like 4.3 years of use. I'm sure by then there will be CS7...so it's a win win I think. Same probably goes for Office 2013. The last version was 2010, so in 2016 when the new Office version comes out, all the subscribers will have access, while those that just bought licenses will have to buy new ones. It is nice that you can decide.