Since the extra pieces libgs and mutool are only used by dvisvgm, they are not installed by default. But they are available in a custom install portion of MacTeX. If you did not use this custom portion and no longer have the MacTeX install package, you can download GhostscriptExtras.pkg. This package installs both libgs and mutool.

Until MacTeX-2025, dvisvgm also required X11. This restriction was removed on 2025 and dvisvgm works regardless of whether X11 is installed or not.

TeX Live contains internal versions of all libraries it uses, so installation of MacTeX does not add any file to /usr/local/lib. But Ghostscript-Extras adds three symbolic links to /usr/local/lib which point to libgs. The actual library is in a subfolder of /usr/local/share. The program dvisvgm should automatically find and use the symbolic link libgs.10.dylib. Thus after installation of GhostscriptExtras, dvisvgm should work without further ado.