dimgui - A port of imgui, the immediate-mode OpenGL GUI library

[Andrej Mitrovic via Digitalmars-d-announce]

If you need a very minimal but usable GUI library for your OpenGL
applications, then an immediate-mode GUI such as IMGUI could be just
the trick. IMGUI has been ported to D and can be found at the
following links:

https://github.com/d-gamedev-team/dimgui
http://code.dlang.org/packages/dimgui

dimgui is zlib-licensed.