I think this is probably user error, although it probably results from bad interface design on our part. If you go into Preferences -> Directories, there's the list of shared directories.
Many people might think that they should double-click a directory to expose its subdirectories, to navigate to the directories that they really want to share. However, double-clicking a directory name tells aMule to share that directory! The shared status of the directory is indicated by the name being drawn in bold. For the root directory ("/"), that visual distinction is very, very subtle.
So, I'd recommend that you go into that preferences pane and double-click on the root directory a few times to toggle it back and forth, watching for the subtle change. Make sure you leave it in the unbold state, if you don't want it shared.
