Comment 2 for bug 386325

How do you launch Fusion Icon? If you don't do so from the menu entry (which uses the --no-start) entry, it's supposed to start the window manager which was running the last time you used Fusion Icon.

But yes, having it start Metacity if the last time you used it you were on Compiz, if that's a case, is indeed a bug (either in Fusion Icon or in Compiz).