Glacier UI is the next interface for Nemo Mobile. It is a new UI, created and built by the community, and made with the latest technologies like Qt 5 and Wayland.
For development please start with SDK. Window manager is build on lipstick and glacier-home. Lipstick is a project aimed at offering easy to modify user experiences for varying mobile device form factors, e.g. handsets, netbooks, tablets.
For developing of applications please look at Components.