Even though PC5250 is really just telnet with odd key-mappings, IBM doesn't use SSH w/OS/400 that I know of. Before they [link|http://as400bks.rochester.ibm.com/pubs/html/as400/v5r1/ic2924/index.htm?info/rzain/rzainrzaincapi.htm|used SSL] was used IBM had no security at all for Client Access.

Looking around, I see [link|http://javassh.org/|javassh] - does that help?