It is basic and has at least some inaccuracies. I skimmed it and found:

"The NTP protocol was originally developed for the LINUX operating system. "

Kids these days.... so much history lost.

For those under 60 revolutions of the sun: NTP and related protocols far pre-date Linux. Linux is a relatively late arriving implementation of Unix. The vast majority of intellectual property behind Linux was from prior variants of Unix; Linux was just a free, unencumbered version that was widely adopted.