NumFOCUS is a nonprofit organization that promotes and supports open source scientific computing projects, such as Jupyter, Julia, and NumPy. NumFOCUS affiliate projects are “scientifically oriented, open, and kind,” which means they contribute to the advancement of scientific research, are published under a standard open source license, seek engagement with the public, and openly state their values and standards for the project community. MFEM, a scalable finite element methods library led by an LLNL team, was recently selected to join the list of NumFOCUS affiliate projects, broadening the project’s exposure and potential user and contributor community.