NC JFET switch with only one voltage source
simulate this circuit &ndash; Schematic created using CircuitLab

Yes, you can, but it's a bad idea.  If you pull down the datasheet for the JFET used in the example on learning-about-electronics, you'll find that it's designed to be an RF amplifier.  (Note for example the Iss for zero volts Vgs is maximum 20mA ... ).  By holding Vs a few volts above ground with a small 5.1 V zener (switching to a much higher Vss), you can now have a reasonably high Vds even with a series LED and can pull the gate "well below Vs" to switch off the transistor.  Sometimes you will want a resistor between gate and source (as in this example) ... there is a small finite capacitance between the gate and source, and adding a resistor will help carry away that gate charge.  Even if you leave it out, there will naturally be some leakage which will dissipate it naturally.