GoodSync automatically synchronizes and backs up all your photos, music, email, and other important files between all your desktops, laptops, servers, and external drives.
Version 11 has been released, see its New Feature List
GoodSync2Go for Mac runs off portable hard drives and USB drives.
Shell script for GoodSync deployment on Mac operating systems.
Enterprise Workstation (Business Client) version of GoodSync implements Policies that allow SysAdmin to limit what users can do.
No limit on users and simultaneous connections.