@Pomegranatepirate @gemlog what do you want to install on your Mac? There are multiple options. Some GitHub repos offer already compiled Binaries (that's the readymade executable program) that you can just download and unpack and start.
If they offer only the source code ... then it's getting complicated. While you can install the macOS development tools on your Mac, compiling software isn't trivial and might not work if the source code isn't already prepared for macOS.
A good way to start getting OpenSource software on your Mac is Homebrew. That's a little tool you install and use as a package manager. You tell it which piece of open source software you're looking for and if there is a "formula" then homebrew installs it for you.