bug#41747: 27.0.91; Add default fontset setup for "Symbols and Pictographs Extended-A"

["Kévin Le Gouguec" <kevin.legouguec@gmail.com>]

Richard Stallman <rms@gnu.org> writes:

> This sounds like a possibly important issue, though perhaps mostly
> independent of Emacs.  Would someone who knows the Symbols situation
> well please offer to explain this to me?

Here's my attempt at a summary; corrections welcome:

- Up to 2018, the Unicode Fonts for Ancient Scripts (UFAS) project
  released its fonts under terms that suggested a free license[1]:

- One of these fonts, Symbola, has an exhaustive coverage of Unicode
  "symbol" characters, so exhaustive that we use it in our default
  fontset for various "symbol subgroups"[2].

- In 2018, the license for UFAS has changed to the document I referenced
  in my earlier message[3].

- Most GNU/Linux distributions reached the same conclusion: the terms of
  this new license does not allow redistribution under any way, shape or
  form[4].  Therefore, these distros now only ship the last free-license
  version of Symbola.

- New versions of Unicode have come and gone since then; they have
  introduced new blocks and new characters (cf. the initial bug report).

- Newer versions of Symbola have followed like clockwork to cover the
  latest "symbol" characters.

- Unfortunately, these new versions fall under the new, non-free
  license.  IIUC this makes them unsuitable for Emacs's default fontset.


Distro developers have reached out to the UFAS developer (as recently as
two months ago for Gentoo[4]; see also Fedora thread linked earlier),
but they could not convince him to switch back to a free license.


[1] The terms have changed over the years; see for example:

https://web.archive.org/web/20150316132421/http://users.teilar.gr/~g1951d/

> *in lieu of a licence* Fonts and documents in this site are not pieces
> of property or merchandise items; they carry no trademark, copyright,
> license or other market tags; they are free for any use. George Douros

https://web.archive.org/web/20180212144935/http://users.teilar.gr/~g1951d/

> In lieu of a licence; fonts and documents in this site are free for
> any use; George Douros

[2] M-x find-library RET fontset RET C-s Symbola

[3] https://dn-works.com/wp-content/uploads/2020/UFAS-Docs/License.pdf

[4] In my earlier message I linked to the relevant NixOS, Arch Linux and
    Fedora threads; for good measure, here are Debian, Ubuntu and
    Gentoo:

    https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=897047
    https://bugs.launchpad.net/ubuntu/+source/ttf-ancient-fonts/+bug/1824065
    https://www.mail-archive.com/gentoo-dev@lists.gentoo.org/msg88799.html