Adobe Flex 2 SDK is free

The Flex SDK is a free tool that will allow you to create Flex & Actionscript 3.0-based applications, without the need to purchase Flex Builder.

Essentially, the SDK contains everything you need to get started developing your own amazing Flex applications. Everything but an IDE (Integrated Development Environment). Now, really all you need to start writing code is a text editor. Though, to be really productive, a great IDE is the way to go. These help to keep your code organized, provide code hints, make compiling & testing easier, and generally make for happier developers.

The Flex SDK consists of a few things:

• mxmlc – This is the command-line based application used to compile your code into the swf files that comprise your applications
• compc – This compiler is used to produce Flex components
• fdb – A command-line based Flex debugger
• The Flex framework files needed to develop a Flex application
• Flash Player 9 – both a standalone version and browser plugin. These are debugger versions of the Flash Player
• A series of JAR files used by the Java-based compilers
• Folders containing links to Flex development resources, html templates for deploying your applications, and sample source code to help you get started.