synergy 1.4.18-r2250 - The last free (gratis) synergy available
Or is it: https://github.com/symless/synergy (source code of newest versions available there)
Synergy brings your computers together in one cohesive experience; its software for sharing one mouse and keyboard between multiple computers on your desk. It works on Windows, Mac OS X and Linux allowing you to seamlessly move your mouse cursor between all computers on your desk.
Website: https://symless.com/synergy/
Last free (gratis) downloads: http://synergy-project.org/download/free/ (No longer there)
Help: https://symless.com/synergy/help
Wiki: http://synergy-project.org/wiki/ (No longer there)
How to compile: http://synergy-project.org/wiki/Compiling (No longer there)