Dia is a free open-source program for designing and building technical diagrams. It is fairly easy to use and can be installed on macOS, Windows, and Linux.
Read about Dia 's features, license, platforms, and more.
Pencil is built for the purpose of providing a free and open-source GUI prototyping tool that people can easily install and use to create mockups in popular desktop platforms.
Read about Pencil 's features, license, platforms, and more.