This google group is retired. At one point new posts were locked, it seems that came undone somehow. I've relocked it.
Please post how-to questions to Stack Overflow, tagged apostrophe-cms so that everyone can find the answers.
But to quickly answer your questions: Xcode is Apple's official package to make it possible to compile open source software on a Mac, without it you can't effectively use Homebrew, which is how open source is usually installed on a Mac. I don't know what alarming reviews you're referring to but this is about having access to Xcode's command line tools, so those reviews probably aren't apropos.
You do not need Xcode on a production server, your production server will probably be Linux and that's a completely different situation. See our production HOWTO:
Hope this is helpful!