Do you know of any other implementations of the rsync algorithm other than the actual rsync program? And where are they used? Do you know how and where dropbox

Do you know of any other implementations of the rsync algorithm other than the actual rsync program? And where are they used? Do you know how and where dropbox uses rsync? There have been some tries to port the rsync program to other languages/platforms [1], but they are usually not in sync with the current rsync program. I am talking about ports of the program, not new implementations of the algorithm. [1] https://github.com/MatthewSteeples/rsync.net https://github.com/MatthewSteeples/rsync.net