Office 356 Small Business Premium, for example, will cost $12.50 per month, or $150 annually, per user, for the right to run Office on up to five devices, effectively granting five licenses to that worker. One of those five licenses could conceivably be used to "unlock" a Surface RT tablet's copy of Office 2013 RT for business purposes.

Microsoft has said that those devices can include "select mobile devices" but has not defined what those devices will be.

Another option: Buy a copy of Office Standard 2013 or Office Professional 2013. While neither have been released, the pair will sell for $369.99 and $499.99, respectively. The cheaper $219.99 Office Home & Business 2013, while licensed for commercial use, won't unlock Office 2013 RT.

As Direction on Microsoft's Miller so succinctly put it: There is no such thing as a free lunch.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at , on or subscribe to . His email address is .