[super_mario]

Yes, it is. But on the other hand it is more discoverable. All I had to do is type "mac os x source code" in google search. It is a little harder to find out about apt-get source coreutils.

First of all you need to know about apt-get. Then you need to know that ls lives in coreutils etc.

[kragen]

You don't need to know that ls lives in coreutils; dpkg -S /bin/ls tells you that, although it is true that you have to learn a little bit about how dpkg and apt work to get to that point. You do need to know what package ls lives in to figure out which tarball to download from Apple's web site.