Rectangle - Window management app based on Spectacle, written in Swift.
Wayland - Wayland is intended as a simpler replacement for X, easier to develop and maintain.
AquaSnap - Too many windows on your screen? Stop wasting your productivity.
Y Window System - Y Window System is a platform that allows you to improve the speed, working, and efficiency of the application in your operating system and helps you to increase the responsiveness of applications similar to any locally based app.
WindowGrid - Quickly and easily layout windows on a dynamic grid using just the mouse.
XQuartz - The XQuartz project is an open-source effort to develop a version of the X.