I won't blame you for the confusion, as the naming is mixed up, but "Flex SDK" is the command-line Flash (SWF) compiler. It's free and open source. It's used to

I won't blame you for the confusion, as the naming is mixed up, but "Flex SDK" is the command-line Flash (SWF) compiler. It's free and open source. It's used to create SWFs or SWCs. It's the same compiler the Flash IDE has built-in. I create full, rich Flash content with the Flex SDK, and has been doing it for a while. I don't compile with the Flash IDE. Not because I can't or because it's paid, but because using Flex SDK is better.