Change the Button Lenguage

It depends on which button(s) you are talking about. I just checked and the Login button looks like it uses this language file:
en-GB.mod_jfbclogin.ini

If you are talking about other buttons, let me know and I can investigate. If they aren't using a language file, we will put it on the list of changes for the next release and help you change it temporarily until them.

Thanks for your help.