Leafnode is a USENET software package designed for small sites, with a
few tens of readers and only a slow link to the net.

Only groups that someone has been reading in the past week are fetched
from the upstream NNTP server.  When someone stops reading a group,
fetchnews will stop reading that group a week later (this is the default
which can be configured), and when someone starts reading a group, fetchnews
will grab all the articles it can in that group the next time it runs.