I converted the source code for the recent release of Flashbuilder 4. I remember that I had to change references to FlexGlobals.toplevelApplication.... There were some other problems, but nothing major.
If you are still interested, post the errors that you get when you try to compile and I should be able to look at those lines of code in my source and let you know what I did. I can't send you the modified source files, but I would be happy to send you individual lines.
I assume Drumbeat will have a FlashBuilder 4 version available soon, now that it has officially been released.
Why do you say the project is dead?
I personally have reservations about Adobe trying to put a full HTML Page Renderer into the Flash Player runtime.