[Other] Migrate Kipper project license from `GPL-3.0-or-above` to `EUPL-1.2`

[Luna-Klatzer]

Is there an existing issue for this?

• I have searched the existing issues

Current State & Issue

Since the release of the EUPL-1.2 (European Union Public Licence) by the European Commission in 2017, there has been a significant argument for the adoption of the EUPL as a European license intended to foster FOSS projects and seamless technical interoperability, whether they're from public European institutions or private individuals.

With the large amount of detailed license information, license translations in 23 European languages and common license interoperability charts provided by the European Commission on their Interoperable Europe Portal, the EUPL seems to be a solid choice for any European FOSS project.

Going forward, as Kipper is a public non-restricted FOSS project, adopting the EUPL as the primary license would not only bring various established ecosystem benefits but also allow for various integrations of Kipper if one desires to do so. This includes various downstream license compatibility options that can freely use Kipper and license their projects under their own FOSS license.

Additionally, as a replacement for the current license GPL-3.0, which is generally considered fairly restrictive, the EUPL would serve as a freer and more integrable license, which does not compromise on the main aspects of a copyleft FOSS license.

Still, as Kipper is under development and not a fairly active project, changing the license is not a priority for now, as access to the project would also not significantly change between GPL-3.0 and EUPL-1.2.