The Two-Layered GUI Toolkit is a library of GUI helper classes which is designed in a way to simplify development of separate interchangeable front-ends. For every supported dialog box type, there is a settings class (independent from a GUI toolkit) whose options can be used by one of the implementations for a specific GUI toolkit (bindings for Gtk#, WPF, and WinForms are provided, but custom ones can be added). That is, the dialog definition can be prepared by the application's core component and passed to the front-end, which uses it to instantiate the dialog box using whatever GUI toolkit it likes.
Revised is a visual editor (or wizard/assistant/GUI) for Ren’Py, the visual-novel game editor. Ren'Py has a lot of capabilities, and Revised's purpose is not to allow everything that Ren'Py can do, just some of the basics. You can think of it as a step-by-step wizard to create the skeleton of a Ren'Py game.