zeptodb is a small collection of relatively tiny command-line tools for interacting with DBM databases.
DBM databases are flat (non-relational) a databases; in other words, they are persistent key-value hash tables. Typically they are created via a library for C, Python, Perl, etc. These tools fill in a gap by providing useful command-line tools for creating and manipulating such databases. Some DBM libraries come with really basic binaries for manipulating the databases, but they are not designed to be very flexible or useful in the real world.
These tools may be helpful in scripts, for example, when persistant data storage is needed but when a full database would be overkill. DBM databases offer a constant look-up time for any record in them, as opposed to, say, searching through a text file, which scales linearly with the number of lines in the file. Thus, scripts requiring fast data look-up would benefit greatly from them. These commands may also be useful if, for whatever reason, one would like to manipulate, via the command-line or scripts, DBM databases created by other programs.