  We present the first comprehensive search for submillimeter and radio
emission from the host galaxies of twenty well-localized gamma-ray bursts
(GRBs). With the exception of a single source, all observations were undertaken
months to years after the GRB explosions to ensure negligible contamination
from the afterglows. We detect the host galaxy of GRB 000418 in both the sub-mm
and radio, and the host galaxy of GRB 000210 only in the sub-mm. These
observations, in conjunction with the previous detections of the host galaxies
of GRB 980703 and GRB 010222, indicate that about 20% of GRB host galaxies are
ultra-luminous and have star formation rates of about 500 M_sun/yr. As an
ensemble, the non-detected hosts have a star formation rate of about 100
M_sun/yr (5-sigma) based on their radio emission. The detected and ensemble
star formation rates exceed the optical values by an order of magnitude,
indicating significant dust obscuration. In the same vein, the ratio of
bolometric dust luminosity to UV luminosity for the hosts detected in the
sub-mm and radio ranges from 20-800, and follows the known trend of increasing
obscuration with increasing bolometric luminosity. We also show that, both as a
sample and individually, the GRB host galaxies have bluer R-K colors as
compared with galaxies selected in the sub-mm in the same redshift range. This
possibly indicates that the stellar populations in the GRB hosts are on average
younger, supporting the massive stellar progenitor scenario for GRBs, but it is
also possible that GRB hosts are on average less dusty.
