From https://alliance.seas.upenn.edu/~bcpierce/wiki/index.php?n=M...

"Rsync is a mirroring tool; Unison is a synchronizer. That is, rsync needs to be told "this replica contains the true versions of all the files; please make the other replica look exactly the same." Unison is capable of recognizing updates in both replicas and deciding which way they should be propagated."

Larry - would you please email us at info@rsync.net ? We have a few items to discuss with you ...

(your profile mentions to respond to one of your comments if someone needs to reach you ...)

A new version has been released this year. unison works remarkably well, it's understandable there is not much to add.