freesurfer is built for Intel macOS and so requires Rosetta 2 to be installed.
You can install Rosetta 2 with:
softwareupdate --install-rosetta --agree-to-license
Note that it is very difficult to remove Rosetta 2 once it is installed.
The vendor offers a free license for freesurfer at:
https://surfer.nmr.mgh.harvard.edu/registration.html
