Double Commander is a cross-platform open source file manager with two panels side-by-side. It is inspired by Total Commander and features some new ideas. Here are some key features of Double Commander:

ForkLift is a robust and elegant Finder replacement and FTP + SFTP + WebDAV + Amazon s3 client, fully embracing the Apple methodology of bringing incredible power to a beautiful and easy-to-use, approachable interface, it also integrates multiple features you would normally buy in many separate applications. Batch Rename, App Deleter, Archive creation & management, powerful Folder Sync, and the ability to Split and Combine large files are all at your fingertips.