Mathics is a general-purpose computer algebra system (CAS). It is an open-source alternative to Mathematica. It is free both as in "free beer" and as in "freedom".
PennyLane is a cross-platform Python library for differentiable programming of quantum computers. Train a quantum computer the same way as a neural network.
CKAN: The Open Source Data Portal Software CKAN is the world’s leading open-source data portal platform. CKAN makes it easy to publish, share and work
CONCEPT (COsmological N-body CodE in PyThon) is a free and open-source simulation code for cosmological structure formation. The code should run on any Linux system, from massively parallel computer clusters to laptops.