NEW YORK ( TheStreet) -- Finally, after months of hints and rumors, Microsoft ( MSFT) has released a version of its Office suite optimized for Apple's ( AAPL) iPhones -- but not for iPads. The official name of the app is "Office Mobile for Office 365 Subscribers," and that name tells much of the story. The app is available as a free download from Apple's iTunes Store. However, to use it you must be a subscriber to Microsoft's Office 365 online service. The service can cost as little as $4/month for business email, to $100 for as many as five home users up to $450 per year, per user, for Office Professional 2013 access. Users who are already Office 365 subscribers will be able to use the app on as many as five iPhones in addition to other devices. The app will allow users to read, compose, edit and store documents in Microsoft Word, Excel and PowerPoint formats. That includes documents in Microsoft SkyDrive or SharePoint system. Apple warns potential users that "Microsoft Office 2013 on a PC is needed for features like recent documents and resume reading." Although the app is free to download, Apple will reportedly still be making money from its use. It is believed that instead of the usual fee charged developers, Apple will, instead profit from the app accessing Office 365 for the first time. Exact details of the fee structure were not disclosed. Apple says the new software is optimized for the iPhone 5, but will also work with previous iPhone 4, iPhone 4S and 5th generation iPod touch devices (iOS 6.1 or later. In early morning trading, Microsoft was trading at $34.50, down 0.62% while Apple was off 0.29% to $434.69. -- Written by Gary Krakow in New York. >To submit a news tip, send an email to: email@example.com.