Azul.rs is described as 'Azul is a free, functional, immediate-mode GUI framework for rapid development of desktop applications written in Rust, supported by the Mozilla WebRender rendering engine' and is an app in the Development category. There are four alternatives to Azul.rs for Linux, Mac and Windows. The best alternative is Sauron native, which is both free and Open Source. Other great apps like Azul.rs are Conrod (Free, Open Source), OrbTk (Free, Open Source) and WebRender (Free, Open Source).
The Orbital Widget Toolkit is a multi platform (G)UI toolkit for building scalable user interfaces with the programming language Rust. It's based on the Entity Component System Pattern and provides a functional-reactive like API.