Inquiry: FreeBSD Handbook Section 1.2

[Fred Pohls]

Thank you all for your hard work on this world-class piece of technical
writing. To have a handbook that isn't a wiki or badly formatted
amalgam of HTML and duct tape is a godsend.

I have more or less a question about licensing and copyright pertaining
to Section 1.2 of the FreeBSD Handbook. The second paragraph mentions
AT&T UNIX® not being open source, but what largely consisted what was
historically cconsidered "AT&T UNIX®" is all but nonexistent, instead
effectively existing as the SUS/POSIX standard. It's my understanding
that Caldera International opened the source code to 7th Edition
Research UNIX under permissive licensing, and thus, as free software.

What's the reasoning behind the Handbook still using this nomenclature?
Is it for historical reasons, or as terminology pertinent to the
discussion of FreeBSD as a derivative of the historical Berkeley UNIX,
as opposed to a System V-style system? 

Again, thank you.

Fred Pohls
Telecommunication Student
University of Florida, '21