How to "Mirror" or "Split" bar code data scanned by one USB scanner to two computers using Y cable?
If you want to have your USB attached scanner to be used either by one computer or by the another one, then you can connect it to a small embedded system running USBIP, and then connect to that device via network from the currently used computer.

It can be done e.g. using the USB equipped wireless access point with reflashed 
OpenWRT firmware, like described here.

It is not possible to use that scanner simultaneously from both computers.