Free and Open Source software was at the center of the first image of a black hole. The team used three different imaging software libraries to achieve the feat. Out of the three, two were fully open source libraries – Sparselab and ehtim.
Sparselab is a Python Library for Interferometric Imaging using Sparse Modeling. ehtim is a Python module for simulating and manipulating VLBI data and producing images with regularized maximum likelihood methods. Richard M Stallman, the founder of the GNU Project will be glad to see that the source code for both libraries is released under GNU GPL v3.