Missing copyrights for icons

[stefan6419846]

The icons in https://github.com/pradyunsg/furo/blob/main/src/furo/assets/styles/variables/_icons.scss are attributed to two different sources, but are missing their original copyright notices.

• The search symbol refers to https://tablericons.com/, where the source is available at https://github.com/tabler/tabler-icons Its license (MIT) requires including the original copyright notice inside the distribution: https://github.com/tabler/tabler-icons/blob/main/LICENSE
• The other icons refer to https://squidfunk.github.io/mkdocs-material/reference/admonitions/ I guess the source files are at https://github.com/squidfunk/mkdocs-material/tree/master/material/templates/.icons(?) They have differing icon licenses (CC-BY-4.0, Apache-2.0, MIT or CC0-1.0, depending on the third-party icon set), usually requiring proper attribution and possibly including the original notice.

As it stands, this violates the icon licenses and should be updated once it has been determined what the actual original source files are.

[stefan6419846]

I just did some more digging about the admonition icons, and it is getting more complex:

• From

  furo/src/furo/assets/styles/variables/_icons.scss

  Line 8 in 12f288e

  // Factored out from mkdocs-material on 24-Aug-2020.

  we know that we should look into the version live at 2020-08-24.
• This leads us to https://github.com/squidfunk/mkdocs-material/tree/8ee168954f1d2825029a48035a1e4ed74cc68a23/material/.icons, where I could match all icons to ones inside the material directory. We now know that the icons are from Material Design Icons 5.5.55 (https://github.com/squidfunk/mkdocs-material/blob/8ee168954f1d2825029a48035a1e4ed74cc68a23/package.json#L46)
• mkdocs-material has a license file for it (https://github.com/squidfunk/mkdocs-material/blob/8ee168954f1d2825029a48035a1e4ed74cc68a23/material/.icons/material/LICENSE), but this does not correspond to the license for the icon files, but is the one for the corresponding SVG package: https://github.com/Templarian/MaterialDesign-SVG/blob/v5.5.55/LICENSE
• The license for the actual icon files has been changed on 2020-09-09: https://github.com/Templarian/MaterialDesign/commits/master/LICENSE
• For us, the following license file should hold true: https://github.com/Templarian/MaterialDesign/blob/4456d09a1dd147033fc5ba820c773c6c587a9c68/LICENSE (data corresponding to release 5.5.55: https://github.com/Templarian/MaterialDesign/tree/30b85f9e97ee3b1b449677cf45336b65a4e03763)
• This license file refers to OFL-1.1, but mentions that the upstream data is (most likely) Apache-2.0.
• OFL-1.1 is usually unsuitable for standalone icon files, as each modification requires using a new name.

As it stands, we should probably include a coy of the OFL-1.1 and Apache-2.0 licenses for the admonition icons.

[pradyunsg]

A PR for this would be welcome!

[stefan6419846]

I would propose to switch to plain Material Icons, thus retrieving them from Google directly instead of relying on https://github.com/Templarian/MaterialDesign This makes the licensing more clear and avoids the OFL-1.1 license.

Is it okay to have Apache-2.0 licensed code inside this repository? If yes, this would be the easiest approach. Otherwise, we would have to rely on an old Material Icons versions using CC-BY. (For now, I could not find spark.svg there and search.svg and flame.svg would differ a bit.)