This is a bug report on the website. On the page "https://geant4.web.cern.ch/support/download", the URL to download the Low Energy Nuclear Data (LEND) files no longer works.
I have contacted the person at LLNL who manages this.
As you will notice, the link to the LEND data has disappeared from the Geant4 web page. LLNL is working on a new database and in future it will not be accessed buy ftp. In the meantime we plan, upon LLNL approval, to set up a copy of the existing database until the new one is ready. Until we get that approval, you can continue to use the link ftp://gdo-nuclear.ucllnl.org On a Mac you will need to do the following: in Finder, do Go (Connect to Server). Enter the above link there and hit "Connect" In the window that comes up next, connect as "Guest" and then you can get the files.