muCommander is a lightweight, open-source, cross-platform file manager that will run on any operating system supporting Java.

trolCommander is a fork of the free and opensource (GPL) file manager muCommander.

Tux Commander is an opensource GTK2 file manager.

Dolphin is a lightweight file manager. It has been designed with ease of use and simplicity in mind, while still allowing flexibility and customization.

fman is a dual-pane file manager for Windows, macOS and Linux.