Two Way File Sync Utility for Windows, similar to Unison -- 2

We need a Windows file sync utility that does a two-way sync over the Internet, and uses the Rsync protocol to sync the changed parts of files AND entire files (if new files have been added.) AND can delete files if files have been deleted. It needs to trigger Microsoft's VSS if needed to handle open and locked files. Start with an open source project like Unison, but preferably written in C#, Visual Basic, Java, or .NET and able to be compiled for Windows with MS Visual Studio 2013. This is a console application with no GUI. It will be called with parameters on the command line. Extra points if it runs on Mac and Linux, too! We need to do a two-way sync on folders with subfolders on two or more computers connected by the Internet or local network running IP. The utility needs to be smart enough to figure out which files have changed and which way it should sync. Its purpose will be to mirror a server to an offsite location. See Unison and BitTorrent Sync for ideas. We like the features in both of them.