JADE is fully redesigned and more feature complete version of SOSFTP at the same time JADE is backward compatible to SOSFTP.
JADE's application architecture is more open to integrate new Data source/protocols.
JADE also use better and latest java libraries for file transfer i.e. jcraft.
JADE have paradigm shift compare to SOSFTP, where SOSFTP can only send and receive files from host where SOSFTP is installed, JADE can transfer file from server-to-server, without touch down. For JADE 's operation term everything is copy and move operation i.e. if user want to send files from host where JADE is installed to remote host via FTP , JADE's "source" will be localhost and "target" will be FTP server.
if user want to receive files from remote FTP server , now "source" will be FTP server and "target" will be localhost.
Apart from architecture improvements JADE have major bug fixes, performance improvements.
SOS has stop ongoing development on SOSFTP and all the ongoing efforts are concentrated on JADE