According to the report, the app will be free for viewing, but editing will only be supported for people with Office 365 subscriptions. Users will need to sign in with a Microsoft account to use the free app, whether they have an Office 365 subscription or not.
If this report is true, Microsoft's version of Office for these platforms won't have much to set it apart from other apps that do the same thing. (Microsoft has not confirmed the existence of the app or the timing, saying only that it will support Office across platforms.)
There are already many options for viewing and editing Office documents on the go. My Motorola Atrix 4G came with Quickoffice, which lets me view and edit Word, Powerpoint, and Excel documents. I can save my edited versions to Dropbox, Box, SugarSync, and other online services (although not Skydrive, as Quickoffice is owned by Google.).
Different pro versions of Quickoffice cost $15 to $20 for Android and iOS devices. Apple's iWork, Smart Office, and others offer additional options for viewing and editing Office documents on mobile devices.
Offering Office apps on competing mobile platforms will represent a shift for Microsoft. Back when Windows Mobile had decent market share, it appeared that the company’s strategy was to try to convince mobile workers to use Windows Mobile as the only way to get a mobile Office app from Microsoft. But with the transition to Windows Phone, Microsoft’s mobile market share has plummeted and the company must see that mobile Office isn’t going to draw people to its mobile phone platform.
In addition, the advent of Office 365 means that Microsoft can now more elegantly offer the mobile app to paying Office customers. Office 365 users have a user name and password that they can use to sign in to the mobile app. Prior to Office 365, there hasn’t been a simple way to tie the mobile and desktop versions of Office together.