Apparently, that's not what they mean:

"Flash proxy" is a name that should make you think "quick" and "short-lived." Our implementation uses standard web technologies: JavaScript and WebSocket. (In the long-ago past we used Adobe Flash, but do not any longer.)

http://crypto.stanford.edu/flashproxy/

That's truly unpleasant. I don't get how anybody thinks that is acceptable behavior.

The name is Flashproxy but it doesn't actually use Flash (it used to). It uses WebSocket.