What is it?
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.
What's different?
Whereas Synergy has moved beyond its goals from the 1.x era, Barrier aims to maintain that simplicity. Barrier will let you use your keyboard and mouse from machine A to control machine B (or more). It's that simple.
Project goals
Hassle-free reliability. We are users, too. Barrier was created so that we could solve the issues we had with synergy and then share these fixes with other users.
Compatibility. We use more than one operating system and you probably do, too. Windows, OSX, Linux, FreeBSD... Barrier should "just work". We will also have our eye on Wayland when the time comes.
Communication. Everything we do is in the open. Our issue tracker will let you see if others are having the same problem you're having and will allow you to add additional information. You will also be able to see when progress is made and how the issue gets resolved.