Responding to the edited question, where the OP is emphasizing he wants keystrokes on one keyboard sent via USB to two different machines.

The language you would want to be using in this situation is a USB "splitter". Such a thing does not exist. Although this is conceivable to do in the keyboard example, where information is being passed only in one direction, it would fall apart with other types of USB devices that want to have a conversation with the computer, because it would be ambiguous which of the two computers would respond to the device. You can do splitting with something like a VGA signal because you don't get this sort of conversation going on (even though there is bi-directional signaling going on, it can be handled by a splitter

What you are looking for is a USB "splitter". Such a thing does not exist. Although this is conceivable to do in the keyboard example, where information is being passed only in one direction, it would fall apart with other types of USB devices that want to have a conversation with the computer, because it would be ambiguous which of the two computers would respond to the device. You can do splitting with something like a VGA signal because you don't get this sort of conversation going on (even though there is bi-directional signaling going on, it can be handled by a splitter).