Open365 Is An Open Source Alternative to Microsoft Office 365 (open365.io)
Martin Brinkmann, writing for Ghacks: Open365 is an open source Office 365 alternative that allows you to edit or create documents online, and to sync files with the cloud. The service is in beta currently but you can sign up for it already on the official website. You may use it using a web browser, download clients for Windows, Mac or Linux desktop machines, or for Android. An iOS client is in the making currently and will be made available as well soon. Open 365 offers two main features that you can make use of. First, it enables you to synchronize files between devices you use and the cloud. Second, it allows you to view, edit and create documents in the cloud using the technology provided by the Open Source Office suite LibreOffice Online for that.
The Free software foundation has written a recommended piece as to why you should avoid software as a service and that "open source" software as a service in no way protects users freedom or privacy. Online services should only be used when you want to share information with others. When you are working on data for your own use, their is no point in using software as a service, you give up rights when you do so.
http://www.gnu.org/philosophy/who-does-that-server-really-serve.en.html