"This isn't new," said Miller. "[Office] Home & Student has always had these limitations. The issue arises because it is integrated into Windows RT, and consumers could unwittingly buy a device with Windows RT thinking 'I have Office,' do commercial work on it, and then fail to be within the license guidelines."

Daryl Ullman, the co-founder and managing director of the Emerset Consulting Group, which helps companies negotiate software licensing deals, echoed Miller.

"No, this isn't a surprise. Microsoft has the same rules, although they're named differently, for an Office OEM license," said Ullman in a Wednesday interview, referring to copies of Office that are factory-installed on new PCs. "If Office is pre-installed on a device, [its license] is not sufficient for use in a business."

Microsoft has been making what Ullman called a "very subtle but very meaningful shift" in their licensing policies, edging away from the desktop PC as the center around which licenses revolve, and toward a more inclusive definition that stresses "devices" instead.

"Every device, whether it's a mobile [phone], tablet, desktop, notebook, are now required to be counted in the overall volume licenses [that a company pays for]," said Ullman. That's been driven by, among other factors, the "bring-your-own-device" (BYOD) movement to incorporate employee-owned hardware into businesses, as well as the growth in smartphones and tablets, and a corresponding slump in traditional PC sales.