Do organizations and developers that build applications with Flex need to release their projects as open source?
You do not need to release source code for your Flex application. You are, however, required to release any source code modifications made to the ActionScript source files provided as part of the Open Source Flex SDK. These modifications must be released under the MPL. This obligation does not extend to other files created by you, even if they are combined into a single executable or bytecode file. For a complete explanation of your rights and obligations under the MPL, consult a legal professional.