According to Adobe, they are to release ActionScript components from the Flex SDK,Java code for ActionScript and the MXML compiler. The open sourced Flex SDK will be available under Mozilla Public License (MPL).The MPL will allow full and free access to the source code, allowing developers to download, extend, and contribute to the source code for the Flex compiler and framework classes. This show Adobe's commitment to open technology initiatives, including the contribution of source code for the ActionScript Virtual Machine to the Mozilla Foundation under the Tamarin project. At the same time it also show how Adobe is planning to tackle its rivals like Dekoh, Dojo etc which are already open.
Now Microsoft's Silverlight is yet to see the open source light. And I am sure that's not going to happen. Another set back that Silverlight will have is that, the support for linux (Unless mono project take up the task). So... keeping the heat on RIA technology all these products are going to change our internet experience in next 2 year in a big way!