Flash MiniBuilder is a lightweight IDE created for developing programs written in ActionScript 3.
Flash MiniBuilder is itself written in ActionScript.
Flash MiniBuilder is free and open-source (GPL license)
Two of the main raison d'etre of MiniBuilder are
Extending, changing (and even integrating MiniBuilder with other software) is easy: MiniBuilder is itself written in your favourite language, AS3!
Because ActionScript virtual machine is now an open source project, we expect lots of solutions to adopt it for embedding. From the start, MiniBuilder targets several implementations of Tamarin AVM:
Check the project page
Screenshots on Ubuntu Linux