Adobe Flex is a collection of technologies released by Adobe Systems for the development and deployment of cross-platform rich Internet applications based on the Adobe Flash platform. In February 2008, Adobe released the Flex 3 SDK under the open source Mozilla Public License. Adobe Flash Player, the runtime on which Flex applications are viewed, and Adobe Flex Builder, the IDE built on the open source Eclipse platform and used to build Flex applications, remain proprietary. The Flex SDK provides a productive, open source framework for building and maintaining web applications that deploy on all major browsers, desktops and operating systems.