rsync is a software tool for synchronizing data across locations. You can use it to download and keep up to date a copy of the BMRB archive.
Run this command to download the BMRB macromolecule archive:
rsync -avh rsync://www.bmrb.wisc.edu:/bmrb_entries/ bmrb_entries
Run this command to download the BMRB metabolomics archive (including time domain data):
rsync -avh rsync://www.bmrb.wisc.edu:/metabolomics_entries/ bmrb_metabolomics
To update your local copy, simply run the same command again from the same directory.