And here it is:
http://code.google.com/p/chumbydevelop/
Tomorrow I'll try to write some documentation, but basically all you need to do is install FlashDevelop 3 and then copy the folder "03 ActionScript 2 - Chumby" in C:\Documents and Settings\<user>\Local Settings\Application Data\FlashDevelop\Templates\ProjectTemplates
If the template would come preinstalled with FD it would be in C:\Program Files\FlashDevelop\FirstRun\Templates\ProjectTemplates, but I don't know if there is a way to tell FlashDevelop to re-scan the source template folders.
Once you have the template, run FlashDevelop, select "New Project" and you should see "Chumby" in the list of templates for ActionScript 2. Select it, give a name to the folder and the project and go.
Build the project and test it, it should display a text message on a blue background. If that works, just go ahead and build the real app.
Note: I chose to copy all the "util" files (UI, Chumby and widgets) into each project. It makes everything easy.
Mtasc is smart enough to only compile the files you use so extra sources don't make your app any bigger.
And you can always remove the files you know you will not be using.
Enjoy and let me know what you think!