Ajaxian » Adobe Open Sources JavaScript Engine in Mozilla Foundation I really don't know what this means yet, but it certainly is exciting news. ActionScript is the ECMAScript implementation Adobe uses in its Flash engine. As I understand it, one benefit over the JavaScript engine now used in Firefox is that ActionScript is compiled to bytecode, so can run more efficiently. Obviously, it's also optimized for talking to Flash objects, but this news doesn't mean Adobe has open-sourced Flash. Which is too bad, actually. But I need to do more reading to understand fully what's going on. There's a good article on the topic here, and the home page for Mozilla's new Tamarin project is here.