WARNING: It is still somewhat buggy (2.0.3). (This is still true in 2.1.0; for example, it doesn't support comments about files, and it crashed on me a few times. If only it worked, it would be a great way to have aMule run all the time in the background, as a daemon, with the GUI coming and going as you like.)
NOTE: You must have External Connections enabled in order to be able to connect to aMuled. More important, you need to set a password for the connections. And if you only want to control it from the local machine, set the interface address to 127.0.0.1 (the loopback interface), which can only be reached from the local machine.
See also aMuleGUI FAQ.