Barrier is a cross-platform software utility for sharing your mouse and keyboard between multiple computers on your desk. It was forked from Synergy version 1.9's codebase.
Barrier vs Synergy opinions
It's a fork of the original version and is maintained.
open source, actively updated
It just works, can be set up very fast and works perfectly
Is free and open source, works perfectly between my Linux machine and Windows laptop, other than entering an IP and dragging a monitor icon, practically no setup was needed
Sleek, fast, secure and open. No magic behind the scenes and it Just Works™. Can't recommend this enough!
Works flawlessly, little setup required.
It's open source and works flawlessly !
Input Leap is software that mimics the functionality of a KVM switch, which historically would allow you to use a single keyboard and mouse to control multiple computers by physically turning a dial on the box to switch the machine you're controlling at any given moment.
This program will let you use two screens on two different computers as if they were connected to the same computer.Discontinued
The project is no longer developed but the program is still downloadable and working
x2vnc (win2vnc) vs Synergy opinions
This does not actually replicate the functionality of Synergy
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.
This program will let you use two screens on two different computers as if they were connected to the same computer. It even works between different operating systems.Discontinued
Last Update: 2015-09-23, see https://sourceforge.net/projects/win2vnc/