The secondary Netduino Go will be receiving hub profile commands, just like a physically-connected hub. That profile will wrap other gobus packets so that they make it to their destination (which can be directly connected to the hub or can be downstream even farther).
How much of this is based in C# serial code vs. using Zigbee source / destination configuration?
Is this approach XBee specific?
Are there any other Zigbee compatible devices frequently used in the Arduino/Netduino community which are not XBee?
Could another serial connection other than XBee be used with the code?
Could two Netduino Go boards be wired up over TX/RX for example and use this code?