Docker is a docking application (WindowMaker dock app) which acts as a system tray for KDE and GNOME2. It can be used to replace the panel in either environment, allowing you to have a system tray without running the KDE/GNOME panel or environment.
For comments, see the original dockapps.org entry.
This dockapp is not maintained by the Window Maker Developers Team. Please visit the dockapp's website for downloads.