Widespread implementation of rsync

[Java Dukes]

I came to know about rsync algorithm for transferring files few days ago.  The algorithm provides an efficient way to transfer files from one computer to another over a slow communication link. But I have been wondering why  don't we see a widespread implementation of rsync in most popular file transfer tools.   I know that the algorithm was conceived by Andrew Tridgell and Paul Mackerras from Department of Computer Science, Australian National University. I was thinking about implementing this algorithm in Java and make it available as a freeware/shareware. I guess I would need some kind of permission/license to develop a program that uses rsync.   I will appreciate if someone on the list could address these questions.   Regards   Waqas