Install old version of Homebrew on Snow Leopard

Don't use Homebrew, use MacPorts!

MacPorts does lots of work to support old versions of OS X. They backport kernel symbols and standard libraries. They maintain bespoke patches and a Snow Leopard build bot. MacPorts might just have the best legacy support of any Mac project under active development, and it's really kind of incredible.

Running Snow Leopard in 2021, and choosing Homebrew over MacPorts, is absolute madness! There is a functionally-equivalent project which actively supports your operating system. Use that one.

If, like me, you're not very familiar with Ruby or curl, here's a verbose (and slightly updated version) to the otherwise excellent answer by @rogerdpack:

1. Download https://github.com/Homebrew/brew/tarball/master in a browser
2. Make sure it's saved in ~/Downloads/ (the name will be Homebrew-brew-[latest version number etc.].tar.gz)
3. Download https://github.com/Homebrew/homebrew-core/tarball/master in a browser
4. Make sure it's saved in ~/Downloads/ (the name will be Homebrew-homebrew-core-[latest version number].tar)
5. Save the install file to a file, by running this command in terminal: curl -o ~/Downloads/install.txt https://raw.githubusercontent.com/Homebrew/install/master/install
6. Edit ~/Downloads/install.txt and A. replace /usr/bin/curl -#{curl_flags} #{BREW_REPO}/tarball/master with cat ~/Downloads/Homebrew-brew-[version number etc.].tar.gz B. replace /usr/bin/curl -#{curl_flags} #{CORE_TAP_REPO}/tarball/master with cat ~/Downloads/Homebrew-homebrew-core-[version number etc.].tar.gz
7. Install by running this command in terminal: ruby -S ~/Downloads/install.txt

In my case, the exact filenames were Homebrew-brew-1.5.14-3-g94c0d83.tar.gz and Homebrew-homebrew-core-b83864a.tar