LimeWire passes queries through Gnucleus (and other clients), and others can pass queries through LimeWire hosts. Noone is using the other part. Its just the Gnutella works.

LW users can download files from other users, but it works just the same in the opposite direction.

LW hosts clustering does not change your horizon, it just makes to percentage of LW hosts in your horizon smaller. Is that a problem?