-sshKey option asks for a private key password even if it is not necessary

[hontvari]

As a more general solution, instead of adding every possible ssh option to fdt, a single fdt option - similar to the rsync -e, --rsh=COMMAN option - and/or environment variable would be better, which may allow to specify a remote shell program along with options.

For example
java -jar fdt.jar -e 'ssh -i otherkey' /hello host:/

Another advantage of this approach is that site specific configurations in ~/.ssh/config would have effect.