Can you please help me with clarification about licensing of Flex SDK. Is it a freeware? What if I am developing some flex components and selling them? Is it legal on that path or I need to sign some agreement for that too?
Also please share details about costing and agreement (if any).
The Adobe Flex SDK 4.6 and earlier is released under the Mozilla Public License. The Adobe Flex SDK is free. I am not a lawyer and you may wish to consult one before determining the licensing of code you write based on the Flex SDK, but in general, you can pretty much do anything you want.
The Apache Flex SDK (4.8 and later) is released under the Apache License V2.0. It is also free. Again, you may wish to consult a lawyer, but in general, you can do pretty much what you want here as well.