Futabally does not have a file in reply mode. You have a few options:

• Ask one of the sites that hacked it to supply you with a script. (I forget what these are anymore, most of them are gone. 4chan uses a private script because all the mod passwords and capcodes are inside the script plaintext.)
• Hack it yourself.
• Use Wakaba, a fine, simple script that looks just like Futabally.