The developer liusega writes:
The other problem with dual extruder is when one hotend is working, the second would cause ooze.
Ooze will make printing model caught a lot of unwanted results.
My solution is letting the second hotend to dock on a metal plate to block hot plastic drops from nozzle.
To do that first the second nozzle need to swing and raise above metal plate.
At the same time one filament need to be caught in between idler and extrusion gear teeth with enough pressure.
All the files and instructions to make Sega can be found at:
Sega extruder in action, the print looks great: