Barrier 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. Barrier does this in
software, allowing you to tell it which machine to control by moving your
mouse to the edge of the screen, or by using a keypress to switch focus to
a different system.

Barrier was forked from Symless's Synergy 1.9 codebase. Synergy was a
commercialized reimplementation of the original CosmoSynergy written by
Chris Schoeneman.