I think the problem is not a language problem but rather both a set-theoretic and a technical issue specific to how NTP works.

Set-theoretic: what exactly is meant by "the pool"?

Is it: a) the set of all NTP servers on the Internet which cooperate with those on .pool.ntp.org, b) the subset of NTP servers with hostnames [0-9]+.pool.ntp.org, c) the subset of NTP servers with (one or more particular) "vendor" subdomains under .pool.ntp.org, d) a particular intersection or union of any of these sets?

Technical: Does the perceived restriction on who may or may not use "the pool" apply to NTP servers which wish to participate in "the pool", or to NTP clients which simply wish to synchronize their clocks?

I've found several documents, from ntp.org as well as from other sources, with varying levels of vagueness and contradictory language.

Some examples:

Server configurations should not use .pool.ntp.org servers (why?): http://www.ntppool.org/join/configuration.html#management-qu...

Client configurations may use .pool.ntp.org servers (when?): http://support.ntp.org/bin/view/Servers/NTPPoolServers

IMHO it is urgent that at least ntp.org official documents use much more precise language, in particular defining what exactly is meant by "the pool".