> was itself arguably a copyright-infringing knock-off.

In US law, there is no such thing. The shape of a glyph (or many) isn't even slightly copyrightable. This is settled law. Fonts (on computers) have a special status that makes them semi-copyrightable in that some jackass judge from the 1980s called them "computer programs" and so they have the same protection as software... but this won't protect against knockoffs.