Please clarify license

[Wuzzy2]

Please specify a clear license for this repository.

Currently, sunfish.lua says: "Code license: BSD".

However, this is ambigious. There are multiple "BSD licenses" with important differences. Please write exactly which of the "BSD licenses" you mean. Ideally, suggest to just paste the license text into a text file called LICENSE.txt and also make a short mention in the README file. Please remember to replace the placeholders.

The two now widely used "BSD licenses" are:

• Simplified BSD License / FreeBSD License ("2-Clause"). Text: https://spdx.org/licenses/BSD-2-Clause.html (FSF comment: https://www.gnu.org/licenses/license-list.html#FreeBSD)
• New BSD License ("3-Clause"). Text: https://spdx.org/licenses/BSD-3-Clause.html (FSF comment: https://www.gnu.org/licenses/license-list.html#ModifiedBSD)

There are other "BSD licenses" around (see here and here) but they rarely used these days or are considered deprecated.

However …

However, it seems this code is directly derived from https://github.com/thomasahle/sunfish, which is licensed GPLv3.
If this code is indeed a derivative work, then this repository should probably be GPLv3 because this is a strong copyleft license.