This is the main page on for the ReadiumJS project, which is developing a JavaScript library and viewer for EPUB 3 rendering optimized for use to render EPUB files directly from websites and in browser-based "cloud" readers. Using ReadiumJS does not require any server-side infrastructure or browser plug-ins. ReadiumJS shares common JS modules with the Readium SDK project which targets native apps. 

A Readium Chrome Extension is also available and can be installed from the Chrome Web Store. Presently (as of Sep. 2013) it has the most EPUB 3 features supported, but is based on an older version of the Readium codebase. In the future, this Chrome Extension will be updated to use the new Readium.js and common JS modules; until then, it is not recommended that developers fork this codebase. A somewhat out of date home page for Readium Chrome Extension, with links to source code, is here

All of the ReadiumJS sub-projects are available under the BSD open source license (Readium SDK components, other than the common JS modules shared with ReadiumJS, are available under a dual license model),