What software do I need to build Flex user interface applications?
A. You can create and deploy Flex applications using only the Open Source Flex 3 SDK or the Free Adobe® Flex™ 3 SDK. For a more productive development experience, you can use Adobe® Flex™ Builder™ 3 software, a powerful, Eclipse based IDE available as a licensed product. For a more productive, higher performing approach to connecting Flex applications to back-end services, you can use BlazeDS, a free, open source Java™ solution. BlazeDS includes both Flex Remoting, which provides binary, serialized data transport and Flex messaging services, offering real-time data push.