The latest version of Mutter can be downloaded from Softpedia
Mutter, a window and compositing manager that displays and manages your desktop via OpenGL, has reached version 3.14 Beta 1.Florian Müllner has announced that Mutter 3.14 Beta 1 has been released, featuring a number of changes and improvements.
According to the changelog, Xsync is now called once per frame, GLSL is now being used by Mutter, gestures and touch events on Wayland are now being handled properly, support has been added for the un-minimize compositor effects, the frame background has been set to None, and backend methods have been added to handle keymaps.
Also, revalidated MetaTextureTower levels are now marked as valid, explicit -backward switcher keybindings are now used instead of <shift>-magic, and various bug fixes and cleanups have been implemented.
Check the changelog for more details about this release. You can download Mutter 3.14 Beta 1 sources right now from Softpedia, but you will have to wait until GNOME 3.14 is out to fully enjoy all these changes. This is just the source package, so unless you really know what you are doing, you should wait for a proper release.
Remember that this is a development version and it should NOT be installed on production machines. It is intended for testing purposes only.