GTK+ (GIMP Toolkit) is a cross-platform widget toolkit for creating graphical user interface. Developed by GNOME Foundation
License: Open Source
Electron (Atom Shell) is ideal for developers looking to create cross-platform applications using web technologies, while GTK+ is a robust toolkit for building native applications with a strong focus on performance and native look and feel. The choice between them largely depends on the specific needs of the application, such as the required functionality and target platform.