  We present GiRaFFE, the first open-source general relativistic force-free
electrodynamics (GRFFE) code for dynamical, numerical-relativity generated
spacetimes. GiRaFFE adopts the strategy pioneered by McKinney and modified by
Paschalidis and Shapiro to convert a GR magnetohydrodynamic (GRMHD) code into a
GRFFE code. In short, GiRaFFE exists as a modification of IllinoisGRMHD, a
user-friendly, open-source, dynamical-spacetime GRMHD code. Both GiRaFFE and
IllinoisGRMHD leverage the Einstein Toolkit's highly-scalable infrastructure to
make possible large-scale simulations of magnetized plasmas in strong,
dynamical spacetimes on adaptive-mesh refinement (AMR) grids. We demonstrate
that GiRaFFE passes a large suite of both flat and curved-spacetime code tests
passed by a number of other state-of-the-art GRFFE codes, and is thus ready for
production-scale simulations of GRFFE phenomena of key interest to relativistic
astrophysics.
