I did read the entire article when I first commented, sorry if I missed the change of name when I re-read it.
That in no way negates my previous point, which is that even an Open-Source licence depends upon having valid copyright. It matters not a jot whether the licences in question is “tame” as you put it, or a full-on commercial pay-through-the-nose licence, if the basic product is PD to begin with, and therefore un-copyrightable.
The very fact that we are having this discussion shows that there is ambiguity, either in this article or in the advertising of this font.