  The Joint Experiment Missions for Extreme Universe Observatory comprises a
collection of complementary missions dedicated to pioneering technologies and
techniques for a future space-based multi-messenger observatory which will have
sufficient sensitivity and exposure to measure properties of extremely rare
ultra-high energy (E>50 EeV) cosmic rays and very high energy (E>100 PeV)
neutrinos. Here we describe a general-purpose software framework designed to
facilitate detailed simulation and reconstruction of events observed by the
various missions using both detection of fluorescence and Cherenkov light
produced when cosmic ray or neutrino-induced extensive air showers traverse
Earth's atmosphere. The software builds on a framework developed by the Pierre
Auger Collaboration. We describe the techniques used to organize contributions
from numerous collaborators, manage an abundance of configuration information,
and provide simple access to time-dependent detector and atmospheric
information. We also explain how we support a multitude of computing platforms,
provide fast installation and maintain the broad testing coverage required for
stability of the large and heterogeneous code base. We provide a few examples
of simulated and reconstructed data gathered by some of the JEM-EUSO missions,
including the EUSO-SPB2 instrument.
