Adobe has open sourced the JavaScript engine in Flash under the auspices of the Mozilla Foundation. I don't think this is all of Flash, but I could be wrong abnout that. (I'm not a big Flash person.) Specifically, they are releasing
the ActionScript™ Virtual Machine, the powerful standards-based scripting language engine in Adobe® Flash® Player, to the Mozilla Foundation. Mozilla will host a new open source project, called Tamarin, to accelerate the development of this standards-based approach for creating rich and engaging Web applications.
The Tamarin project will implement the final version of the ECMAScript Edition 4 standard language, which Mozilla will use within the next generation of SpiderMonkey, the core JavaScript engine embedded in Firefox®, Mozilla’s free Web browser. As of today, developers working on SpiderMonkey will have access to the Tamarin code in the Mozilla CVS repository via the project page located at www.mozilla.org/projects/tamarin/. Contributions to the code will be managed by a governing body of developers from both Adobe and Mozilla.
This code is licensed under the same Mozilla tri-license (MPL/GPL/LGPL) as other Mozilla code. They even beat Java out the door. Isn't that ironic?