Frequency filter - wordfreq (origin and licence)
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Source:    wordfreq 3.1.1 by Robyn Speer, https://github.com/rspeer/wordfreq
           sdist https://pypi.org/project/wordfreq/3.1.1/ (wordfreq-3.1.1.tar.gz,
           SHA-256 7943098975f25c2a70e1151ee5a62083b14a5f86f6cc5703cc9526f716ceb408),
           data file wordfreq/data/large_de.msgpack.gz
Retrieved: 2026-09-27
Licence:   The wordfreq data files "may be redistributed under a Creative Commons
           Attribution-ShareAlike 4.0 license" (https://creativecommons.org/licenses/by-sa/4.0/),
           code under the Apache License 2.0 (wordfreq README, section "License").
           wordfreq contains data derived from Wikipedia, OPUS OpenSubtitles 2018 (with attribution to
           OpenSubtitles, http://www.opensubtitles.org/), ParaCrawl, the Leeds Internet Corpus,
           Google Books Ngrams (http://books.google.com/ngrams) and other sources listed in its README.

Extract:   vendor/wordlists/de/wordfreq-de.tsv ("word<TAB>Zipf value"), made with
           scripts/wordlist-wordfreq-extrait.py: only entries written in lower-case letters a-z, ä, ö, ü
           (no digits, punctuation or spaces), otherwise unchanged. Zipf = log10 of the frequency per
           billion words (1 = rare, 7 = very common). wordfreq folds case and writes "ss" for "ß".

Use:       scripts/build-wordlist.mjs (function deHaeufig) builds haeufig-<length>.txt for the word list
           pages /de/woerter/: word forms of de_DE_frami that occur in this frequency list, without proper
           names (heuristic on the Hunspell flags plus a place-name list from GeoNames, CC BY 4.0, used
           only as an exclusion list), most frequent first. The <length>.txt files and wordle.txt do not
           use wordfreq.

Because haeufig-<length>.txt combines the GPL spelling dictionary with CC BY-SA 4.0 data, these files
are distributed under the GNU General Public License version 3 or later (GPLv3 is a compatible licence
for CC BY-SA 4.0 adaptations, see
https://creativecommons.org/share-your-work/licensing-considerations/compatible-licenses/).
Licence text: COPYING-GPL-3.0.txt.