  We present an open-source update to the spherically-symmetric,
general-relativistic hydrodynamics, core-collapse supernova (CCSN) code GR1D
(O'Connor & Ott, 2010, CQG, 27, 114103). The source code is available at
http://www.GR1Dcode.org. We extend its capabilities to include a general
relativistic treatment of neutrino transport based on the moment formalisms of
Shibata et al., 2011, PTP, 125, 1255 and Cardall et al., 2013, PRD, 87 103004.
We pay special attention to implementing and testing numerical methods and
approximations that lessen the computational demand of the transport scheme by
removing the need to invert large matrices. This is especially important for
the implementation and development of moment-like transport methods in two and
three dimensions. A critical component of neutrino transport calculations are
the neutrino-matter interaction coefficients that describe the production,
absorption, scattering, and annihilation of neutrinos. In this article we also
describe our open-source, neutrino interaction library NuLib (available at
http://www.nulib.org). We believe that an open-source approach to describing
these interactions is one of the major steps needed to progress towards robust
models of CCSNe and robust predictions of the neutrino signal. We show, via
comparisons to full Boltzmann neutrino transport simulations of CCSNe, that our
neutrino transport code performs remarkably well. Furthermore, we show that the
methods and approximations we employ to increase efficiency do not decrease the
fidelity of our results. We also test the ability of our general relativistic
transport code to model failed CCSN by evolving a 40 solar-mass progenitor to
the onset of collapse to a black hole.
