Forked and updated, you can install CalculiX on any modern MacOS (even with M1 chip). I use it successfully for FEM simulations with FreeCAD on MacOS.
Installation is very simple:
brew install namore/homebrew-custom/namore-calculix-ccx
Then select the following Path under FreeCAD settings / FEM / CalculiX / ccx binary path::
/opt/homebrew/bin/ccx_2.17
brew install namore/custom/<formula>
Or brew tap namore/custom and then brew install <formula>.
brew help, man brew or check Homebrew's documentation.