So one might say they should open source the core of Flash, the JIT compiler and virtual machine, and not the parts that are licensed. And you're right, that would be the correct move! They did that in 2006: http://en.wikipedia.org/wiki/Tamarin_%28software%29
They also open sourced the Flex SDK: http://opensource.adobe.com/wiki/display/flexsdk/Flex+SDK
What Adobe needs is a completely new product that is available to consumers for free, has it's source code public and free from patents. This way, Adobe tools can still be sold and used to develop, while the player is ubiquitous and as widely spread as possible. And that's what they're trying to do with HTML5: http://www.adobe.com/solutions/html5.html
Adobe's communication to developers is bad. No one knows about any this. Technology isn't their problem, marketing is.
EDIT: Make link a link :-)