That code is not there in order to be useful to someone.
It's there to meet the liabilities that they have through the licenses for the used open source software. These licenses often say that if you use the software you also need to allow the public to retrieve it. Even more so if you make modifications to it.
That's only true of GPL'ed components shipped as part of Mac OS X/ OS X / macOS. A vast majority isn't - some are BSD and most are Apple originated software under an Apple Open Source License (APSL)
Yeah, that might be true. But if you are a big organization you probably want to have a standardized process on how to handle third party open source software (how to document it, where to store it, etc...).
You can build the code. Might take a little monkeying around with your build environment, but each program should be buildable.
I'm not sure what you think "open source" is or needs to be. We were passing around tarballs over ftp for almost all of our open source software in the past.
I would agree that there are obviously ways in which Apple could participate more in many of the open-source projects they use, but I don't really buy your point - it's literally source code which is open!
The idea is for Apple to release the source for components that are included in macOS, and the license requires publication. There is no obligation (or, I would argue, expectation) to do anything more.
Well. Okay. What I really meant to say is that Open Source - to me at least - can really call itself Open Source if there is a collaborative effort to maintain the code, ideally through a version control mechanism.
For example, Android is not Open Source to me because the code is dropped after the fact.
I find the code very useful. I've checked the Core Foundation sources numerous times when I wanted to know how something was implemented. Apple's documentation is sometimes lacking, and it's great when you run into a problem and you can just read the sources.
Unfortunately, CF is always released pretty late (it's "coming soon" for months), and it would be nice if much more was Open Source.
But I'm happy about every bit of code that's public!
BTW, how useful is this code? Obviously you can't build anything with this. It's useful for auditing, maybe?