I’ve added a page describing rsync access:
Downloading the entire IF Archive
MacOS and Linux come with rsync installed. Windows can install it via WSL or the Chocolatey package manager.
The nice thing about rsync is that it’s incremental. For example, this command will download all the files in games/zcode:
rsync -a rsync://rsync.ifarchive.org/if-archive/games/zcode destdir
It takes about 70 seconds the first time you run it. After that, destdir has the files, so if you re-run the command, it only downloads changed or new files. If nothing has changed, the command determines this and exits immediately.