Meet ownCloud 5, The Open Source Dropbox

ownCloud is a free software suite, written in PHP, that provides file storage, synchronization, and sharing. It provides the same basic features of Dropbox or Box.net. It also provides a whole lot more.

ownCloud was started three years ago when Frank Karlitschek wanted a free software alternative to proprietary solutions. In the time since the project has attracted a dedicated group of core contributors, made several significant releases, and is available in 42 languages. It's also spun off a commercial project to drive development of ownCloud for enterprise users.

The core ownCloud offering is file storage and synchronization. You also get optional contacts and calendar synchronization, if you want to use it. As an open source application, you can install it on any computer you control. This means you know how and where your data is stored, something which existing hosted solutions abstract away from you. Individuals and enterprises can install ownCloud on their own hardware, and define access policies according to their own needs.

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http://techcrunch.com/2013/02/24/meet-owncloud-5-the-open-source-dropbox