Wayland / Weston
Wayland is an open source software product that has been designed from the ground up to be used as a drop-in replacement for the X Window System, which is currently used in 99.9 percent of all Linux-based operating systems.
The project comprises of the main display server, called Wayland, as well as a compositor, called Weston. While Wayland itself is not actually an X11 server, it has been engineered as a compositor's protocol in order to talk to clients like Weston, which can run as an X client.
Wayland can run as a standalone display server on top of KMS (Kernel Mode-Setting) and evdev input devices, as a Wayland client, or as a traditional application meant for the X Window System. Furthermore, Weston can run under KMS or as an X11 client and it is suitable for mobile or embedded devices.
Other possible clients for this groundbreaking, next-generation display server can be another display server, X11 servers (full screen or rootless), or any other standard application. A C library implementation of Wayland is also available.
While Wayland provides all the necessary components for the display server to run properly, the Weston compositor comes with various demo clients, which can be used by developers as examples for building ore complex clients.
The well known and widely used GNOME and KDE Plasma desktop environments will most probably be the first to be ported to the next-generation Wayland display server. However, it will probably take a few years for all Linux application developers to migrate (read: port) their applications to Wayland.
Linux distribution and application developers can find detailed documentation about how to port their apps and operating systems to Wayland on the project's homepage (see above). End users can test Wayland today using the RebeccaBlackOS Linux-based operating system.