Office for iPad, and the newer Office apps for Android tablets - both released in 2014 - require an Office 365 subscription for advanced editing and for commercial purposes. Microsoft confirmed that in a follow-up answer, saying that Office Small's licensing would be 'consistent with those required for Office apps on iPad and Android tablets.' It's unclear what constitutes a 'commercial license,' but one would almost certainly be a subscription to a business-level Office 365 subscription. Business customers must have what Microsoft said is a 'commercial license' to use the Office for Windows 10 apps for work-related purposes.