PlaneShift has an integrated screenshot command:
/screenshot
The latest version even has an additional parameter, to shoot only the 3D look behind the GUI windows (so you won\'t see e.g. the message window in your shot):
/screenshot nogui
The last alternative: Usually, OpenGL windows can be shot by pressing [Alt]+[PrtScr] on your keyboard (to catch only the active window), and insert it into a painting tool (via [Ctrl]+[V] usually).