GoodSync - GoodSync provides highly reliable file backup and synchronization for both individuals and businesses.
Syncthing - Syncthing replaces proprietary sync and cloud services with something open, trustworthy and...
rsync - rsync is a file transfer program for Unix systems. rsync uses the "rsync algorithm" which provides a very fast method for bringing remote files into sync.
arRsync - arRsync is a tool that is designed for macOS that is used for transferring and synchronizing files between a computer and a storage drive.
MirrorFolder - MirrorFolder is a real-time folder synchronization and backup software
DirSync Pro - DirSync Pro: Powerfull synchronization and backup utility. It's portable, easy to use, open source, 100% free, 100% spyware-free, no limitations