Flex / ActionScript 3 Development SDK for Mac / Linux
With the release of Flex beta 2 last week, we also added a new SDK only download. This makes it easy to download and install the SDK on Mac, Windows and Linux (no more install on Windows and copy to Mac).
While this does not provide support for Flex Builder, it does allow you to create, compile and debug your applications on Mac, Windows and Linux using your editor of choice (including Eclipse).
You can download the SDK from here.