Looks like Adobe’s announcement to release Flex Builder as open source may have been required by law, or perhaps a long time planned. We’ll never know. But it is interesting that in the announcement on the home page, Adobe says they will release the source later this year, but in fact, it is already available for download in the ColdFusion Tech Notes section.
Adobe Flex Builder 2 is built on Eclipse 3.1.2, provided by the Eclipse Foundation. Additionally, Adobe Flex Builder 2 contains source code derived from Eclipse code. Both the Eclipse code and the code derived from Eclipse code are made available to the community under the terms of the Eclipse Public License v1.0 that accompanies such code, and is also available at http://www.eclipse.org/legal/epl-v10.html.
The ZIP file linked below contains the Eclipse 3.1.2 code as well as Flex Builder code that is derived from Eclipse code. The Eclipse code that was derived for Flex Builder includes editor code, debugger code, workbench code, and editor and debugger icons.
Download the Flex Builder 2 source code derived from Eclipse (106MB).