the linked artikel is about javascripting via node.js the arduino. bit is the arduino o gadgeteer thing or something completely different from fez and spider ?
There are lots of way to communicate between a MF device and a PC. There is UART serial with RS232 converter, serial to USB module, Ethernet and CDC serial(USB Client) .
Look at the .NET MF and Gadgeteer turorial in the Support area for lots of information.
this page mentions the usb debugging with virtual com channel on the usb client dp module.
that is just what i need.
now you can debug the spider while an other instance of visual studio can debug a program which interacts with the spider on the com port. and that with one usb plug.
ghielctronics solved me problem with this solution.