Apache have made their parity release of the Flex SDK (4.8.0) available here. Quite frankly, the installation looks like a bit of a palaver. There's a nice guide on installation here, but it looks like the easiest option is to use the AIR installer here.

Personally, and with the greatest respect, I'm going to hold off until there's an installer that's a little more, err, 21st century. Having tutorials just to install software takes me back to installing Alias|Wavefront on SGI's back in the '90s - a proper faff!