Genode's GUI stack was redone with its "nitpicker" GUI server to maintain low complexity while adding features like window manager, dynamics, and customizability. The design requirements for their GUI stack were to deliver on security, flexibility, customizability, performance, dynamics, and composability.
Like the redone nitpicker GUI server, the Genode window manager is lightweight (around 2,000 lines of code) and doesn't depend on a C runtime but just the basic Genode API. There's many more details on the Genode GUI architecture for those interested via the project's release announcement.
Genode OS 14.08 also brings pluggable VFS file-system support, C run-time support for time functions, a port of the CPU jitter random number generator, a new port of OpenVPN, networking support for VirtualBox, and much better integration of the Qt5 tool-kit.
Those wishing to learn more about the Genode OS 14.08 release can read the always-thorough details posted at Genode.org.