Last month we wrote about the launch of Office 365 Personal, a lower-cost subscription for Microsoft’s productivity suite. Office 365 Personal comes with licensing for one PC and one tablet, but that raised a pretty big question for some users – “What about my Surface?”

The Surface, for the uninitiated, is Microsoft’s answer to the rise of tablet computing. One of its killer features is a snap-on keyboard that lets you type the way you’d expect to on a laptop. As a result, many consumers are using the Surface more like their primary computer, rather than as an additional device. (Many members of the Aptera team use exclusively Surfaces at work, for example.)

So, if you’re using your Surface as a PC, does that count for your PC license, letting you also use Office on an iPad? Or is it just a tablet and you’ll have to dust off your old tower PC if you want to use Excel in two places?

Microsoft cleared that all up this week, talking with Mary Jo Foley of ZDNet. While the Surfaces were initially only qualified as tablets, Microsoft is changing course and allowing customers the flexibility to choose whether they define the Surface as a PC or tablet.

Here’s the statement Microsoft sent Foley:

“We understand that the convergence of device categories can make it difficult to define some devices, and as a result, we have built in some flexibility for subscription customers. For example, an Office 365 Personal subscriber can define their Surface Pro as either a PC or a tablet.”

The change in policy is a good sign for users, especially those invested in the Surface as a platform. Rather than sticking to their guns and forcing users to conform to their definitions, Microsoft is letting people use their software in the way that works best for them.

As the lines between PC, tablet and mobile get blurred by more powerful portable computers and phones with increasingly large screens, this sort of flexibility could prove very important for Microsoft’s efforts to grow their space in all three of those markets.