these are utilities for archiving and restoring soundfiles. Due to the generally large size of such files these are probably more efficient than tar. In addition a catalog of each tape is kept in your ~/catalogs directory. see the man page of sfbackup nsfbackup etc are for a Sun. There are some diffs here. File 1 is considered as the first soundfile, while in sfbackup etc File 1 is considered the label, and file 2 the first soundfile.
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.