Which does it mean that the Nova pedals have 0 ohm for output impedance?
INPUT IMPEDANCE: The input impedance is designed for instruments with high impedance output as electric guitars, electro-acoustic guitars or basses, electric basses (passive). It is a high value: 1 Mohm (1000000 ohm)
OUTPUT IMPEDANCE: The output impedance depends if you use Stereo or Mono cables. Here it has nothing to do with the Stereo or Mono signal but it is about the impedance. If you use a Stereo cable for the L output (for instance) the output signal from the Nova Modulator will be a low impedance signal BALANCED. In the case the Nova Modulator gives 0 ohm. If you use a Mono cable for the L output (for instance) the output signal from the Nova Modulator will be a low impedance signal but this time UNBALANCED. That means, in this case, the impedance will be higher than the BALANCED one : 225 ohm instead of 0 ohm.
Another question: why the Nova Repeater, the Nova Delay, the Nova Modulator have these 0 ohm impedance but not the Nova Drive? That is because the Nova Drive does not provide unbalanced/balanced possibilities. The sense is the capability of the device to "recognize" and to adapt to the different connection options, balanced or unbalanced and therefore adapt the impedance regarding the connection type.