Double Commander is a twin-panel, cross-platform file manager. Inspired by Total Commander and featuring some new ideas in file management. Double Commander is absolutely free, open source software distributed under the GNU GPL version 2 license.
Some features of Double Commander:
all operations work in the background with threading operations support
tabbed panels interface
extended search function with full text search in any files
multiple files name rename at once
built-in file viewer (F3) to view files of ANY SIZE in hexadecimal, binary or text format
built-in text editor (F4) with syntax highlighting
archives are handled like subdirectories, you can easily copy files to and from an archive
supports WCX, WLX, WDX and WFX plugins from Total Commander (also supports its own DSX plugin format)
Note: the project is under heavy development now, so information presented in this document may be incomplete or irrelevant.