There seems to be some confusion if I understand correctly.
There is a free flexible plugin available for eclipse. Flex was an open source project, and the SDK is available as a standalone plug-in for the Eclipse IDE for free; Yes, for free, for several years now. For obvious reasons, it is not widespread, but it is available. Here is a link explaining the free Flex 4 SDK for Eclipse.
Free flex SDK explanation
Don gallucci
source share