Macromedia and now Adobe have chosen to continue to use a free implementation of their ActionScript interpreter. For this they used the NS4 Javascript implementation up to version 7. Now they use the Tamarin project. The format of the compiled action script is much different since Flash version 9. It includes the ActionScript version 3 which is currently described in what is called the
abcFormat document.
I have a copy available in my project. I hope to find the time to duplicate that information in my own reference later.