I am reporting on how I got the above-mentioned device to bridge two Debian Linux systems. One is a normal system, and the other is my BeagleBoard. In my recent BeagleBoard post, I mentioned patching and installing the necessary plusb.c driver. Once the driver is working, you will have a new usbX network interface (view with `ifconfig -a`). To send packets, I chose IP addresses for my endpoints.
On the BeagleBoard (the interface is usb1; usb0 is taken by a USB ethernet adapter):
ifconfig usb1 10.0.0.1 netmask 255.255.255.255 up
route add -host 10.0.0.2 usb1
On the regular x86 system:
ifconfig usb0 10.0.0.2 netmask 255.255.255.255 up
route add -host 10.0.0.1 usb0
Then it worked. The mailing lists claim this Prolific chip is flaky, but I’ve had good luck so far.
Mostly Ramblings 
Is there a way to do the same in windows? Seems windows forces this chip to use “Windows Easy Transfer” and won’t allow it to be a network adapter.
Unfortunately I have no idea.
Is there any way to this in macOS?
I’ve never tried, and no longer have this specific device.