Tobias here. Seems like `homebrew/cask-fonts` is the best way to go for Homebrew, but even the repo maintainers suggest that submission to Google Fonts is their desired method to be included [1]. Once / if SN Pro garners more mainstream popularity we will start supporting more methods of distribution.

[1]: https://github.com/Homebrew/homebrew-cask-fonts/blob/master/...