REUSE configuration

[v--]

I was recently introduced to the REUSE project, whose purpose is to standardize machine-readable license information, so I experimented with adding a REUSE.toml configuration here. The official reuse tool then took care of downloading the appropriate licenses.

Licensing is complicated, so I tried to follow some practices I have seen through my life, including a dozen-or-some similar configurations I searched through.

@kcroker I was really unsure how to formulate the copyright string, so I chose

Copyright © 2015-2026 Kevin Croker, Ianis Vasilev <ianis@ivasilev.net> and contributors

Please take a look and edit it at will. It is possible to add a multiline copyright notice instead (e.g. see here).

[kcroker]

From what I can tell:

• all code products (including all python in src) will be GPL v3 or later
• a few generated and auxiliary files will be CC0
  What's the invisible font doing?

[v--]

@kcroker

1. Your original code was released under GPL-3, so all subsequent modifications must also be released under GPL-3. The copyright years determine when the license expires. For example, the original license is from 2015, so, in the US, in year 2110 the original (but not today's code) would be considered public domain (this varies by country and has a lot of additional clauses like "author's life + 70 years", so the copyright will likely extend past 2110).

   I decided to include everything in one copyright string (I did not include your email for privacy reasons). Another common pattern is to use multiple strings, e.g. "Copyright © 20XX-20YY Author A and Author B" and "Copyright © 20YY-20ZZ Author C".

2. Generated files are generally uncopyrightable, so CC0 (as the closest we have to a "public domain" license) seems to be recommended in REUSE's documentation. These files are only used for development and/or documentation.

   Some projects like poexam uses GPL-3.0 for both the source code and generated files.

3. I have also marked the invisible font as CC0 because its author made it a public domain work. It can just as well be "assimilated" into the project and relicensed, but I wanted to attribute the original author.

   The font is used to draw text that can be searched, selected and copied. This invisible text is drawn on top of the background image, which contains the actually visible text. The process is explained in the wiki.

   There are alternatives to including a font in the source - OCRmyPDF can generate a "glyphless" font, but it is not a trivial task.