Do you know any good open source library other than Apache commons-net FTPSClient to interact with a FTPS site
Regards,
Take a peek at this comparison chart from JavaWorld. It breaks down all of the types of clients by feature, license, and cost.
As pointed out below, this chart does seem to be somewhat old (from 2003).
I don't know if they are open source but there is a list of some libraries:
ftp4j provides FTPS functionality and is, IMHO, easier to work with than the apache commons ftp client. Ftp4j is under active development (not by me).