From the press release announcing the exciting merger of Open Library of Humanities and Birkbeck College:

The OLH is an academic-led, gold open-access publisher (articles are freely and permanently accessible for everyone, immediately after publication) with no author-facing charges.

OLH’s estimable lead, Martin Eve, continues his noble if quixotic campaign to rescue “gold” from its now-entrenched linkage with the APC. Eve has repeatedly, and correctly, noted that the “diamond” appellation is often used in error (as in this Plan S post):

Diamond, however, is also a category error. While “gold” and “green” open access refer to conditions of availability – at the publisher and in a repository respectively – diamond denotes the financial conditions under which a publisher operates. Hence, while the term is meant to connote a supreme condition in which infrastructure exists transparently without financial demands from authors or readers, it also helps to cement the false certainty, erroneously held by many researchers, that “gold” open access means article processing charges (APCs).

True, but the lexical ship has already set sail. It may be that, logic aside, it’s too useful to have a quick metaphor to make the crucial no-fee vs. APC distinction.