What is x2vnc (win2vnc)?
This program will let you use two screens on two different computers as if they were connected to the same computer.
The program will open a small (one pixel wide) window on the edge of your screen. Moving the pointer into this window will trigger the program to take over your mouse and send mouse movements and keystrokes though the RFB protocol to a VNC server running on another machine. When the pointer is moved back towards the opposite edge on the other screen, the mouse is then released again.
The project is no longer developed but the program is still downloadable and working
x2vnc (win2vnc) Screenshots
x2vnc (win2vnc) information
Comments and Reviews
Said about x2vnc (win2vnc) as an alternative
While the description is a little vague, they seem to imply that your keyboard/mouse input is sent to another PC when you move your mouse into a tiny window on either PC.