I'm not sure about this information because the last time I have used the flash builder into a linux machine was in 2007, but check this out:
It says you will need to use SDK from the command line to build flex application.
Thank u Pablo
But where do i get support after installation of this software?
I was hoping to install open source flex in my ubuntu.
But unfortunately , I find only ways of how to install Flex Builder rather than opensource flex in internet.
There is no open source IDE for flex that I am aware of. You can use the open source SDK/compiler, but it does not provide any editing/development tools. For that you have to buy the tools. If you are happy editing in a text editor, and compiling manually, then the open source/free will work. If you want context sensitive help, and WSIWYG design tools, then you need the paid for tools.
Yes, just the Flex SDK is open source. Adobe Flash Builder IDE is a commercial solution.
If you don't wanna buy the Adobe Flash Builder you can write Flex application through any text editor and to compile it using the command line.