You can find a text list of all the files within /Mods_for_Jenkins/net/shadowfacts/Forgelin and nested folders here: http://downloads.gtnewhorizons.com/Mods_for_Jenkins/net/shadowfacts/Forgelin/?raw
To download /Mods_for_Jenkins/net/shadowfacts/Forgelin and all nested folders with aria2c you can do this:
> curl http://downloads.gtnewhorizons.com/Mods_for_Jenkins/net/shadowfacts/Forgelin/?aria2 | aria2c -c -i -