Licenses and credits

The same list as the app's Settings › About and licenses. This page is generated from the project's license files.

Software, fonts and art

FSRS (Free Spaced Repetition Scheduler): Review scheduling uses FSRS-6 with its published default parameters. FSRS is developed by the open-spaced-repetition project; its reference implementations are released under the MIT License.
Fraunces and Inter: Interface and website fonts, by The Fraunces Project Authors and The Inter Project Authors, under the SIL Open Font License 1.1. The license texts: Fraunces and Inter.
Raven and Odin artwork: The scenes, the ravens and the icon are the Frodi design kit, original work (2026).
Map shapes: Natural Earth (public domain), via the world-atlas package (ISC License).
Voices: Words are read aloud by the voices built into your phone.
Words, lessons, readings and examples: Written for Frodi. Everything is marked unreviewed until a native speaker checks it.

Content sources (82)

Stories retold from public-domain tales, the facts behind World, and the references checked while writing. Unless a source says otherwise, no text was copied: the course is written for Frodi.

Brothers Grimm, Kinder- und Hausmärchen (KHM): Public domain (published 1812-1857) · German; Jacob and Wilhelm Grimm, Kinder- und Hausmärchen: KHM 1 Der Froschkönig oder der eiserne Heinrich, KHM 24 Frau Holle, KHM 26 Rotkäppchen, KHM 27 Die Bremer Stadtmusikanten, KHM 55 Rumpelstilzchen, KHM 83 Hans im Glück, KHM 103 Der süße Brei, KHM 153 Die Sterntaler; Source: https://de.wikisource.org/wiki/Kinder-_und_Hausm%C3%A4rchen
DWDS, Digitales Wörterbuch der deutschen Sprache: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · German; Source: https://www.dwds.de
FluentU blog: German insults: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · German; Source: https://www.fluentu.com/blog/german/german-insults
Mental Floss: hilarious German insults: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · German; Source: https://www.mentalfloss.com/article/573354/hilarious-german-insults
Leyenda de los Soles (Nahuatl manuscript, 1558, in the Codex Chimalpopoca): Quetzalcóatl and the ant at the Mountain of Sustenance: Public domain (16th-century manuscript; traditional Mexica myth) · Spanish; Anonymous Nahuatl author, Leyenda de los Soles (1558)
El Callejón del Beso, traditional legend of Guanajuato: Traditional oral legend (no author; public domain plot) · Spanish; Traditional legend of Guanajuato, Mexico
Bernardino de Sahagún, Historia general de las cosas de Nueva España (Florentine Codex), Book 3, appendix: the dead person's dog and the river on the way to Mictlán; with the figure of the god Xólotl: Public domain (16th-century work; traditional Mexica belief) · Spanish; Bernardino de Sahagún and his Nahua collaborators (c. 1575-1577)
General facts about the Guelaguetza (Oaxaca): dates, name, venue, dances: Facts only (not copyrightable); no text copied · Spanish; Common reference facts (Oaxaca state tourism information, encyclopedias)
Real Academia Española / ASALE, Diccionario de la lengua española (DLE): Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · Spanish; Source: https://dle.rae.es
ASALE, Diccionario de americanismos: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · Spanish; Source: https://www.asale.org/damer
FluentU blog: Mexican Spanish slang: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · Spanish; Source: https://www.fluentu.com/blog/spanish/mexican-spanish-slang/
Maya legend of the hummingbird (the gods make the hummingbird from a last piece of jade to carry thoughts and wishes), Yucatán Peninsula; many modern oral and written versions: Traditional oral literature (public domain); no published text used · Spanish; Traditional Maya (Yucatec) storytelling
Mazatec tale of the possum (tlacuache) who stole fire for people and burned the hair off its tail, Sierra Mazateca (Oaxaca); related versions among other peoples of Mexico: Traditional oral literature (public domain); no published text used · Spanish; Traditional Mazatec storytelling
Jean de La Fontaine, Fables, books I and VI (1668): La Cigale et la Fourmi (I,1), Le Corbeau et le Renard (I,2), Le Lièvre et la Tortue (VI,10): Public domain (17th-century text) · French; Jean de La Fontaine, Fables choisies, mises en vers (1668)
Charles Perrault, Le Petit Chaperon rouge, in Histoires ou contes du temps passé (1697): Public domain (17th-century text) · French; Charles Perrault, Histoires ou contes du temps passé (1697)
Wikipedia: Quebec French profanity: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · French; Source: https://en.wikipedia.org/wiki/Quebec_French_profanity
Wikipedia: Verlan: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · French; Source: https://en.wikipedia.org/wiki/Verlan
Wikipedia: Swiss French: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · French; Source: https://en.wikipedia.org/wiki/Swiss_French
Larousse, dictionnaire de français en ligne: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · French; Source: https://www.larousse.fr/dictionnaires/francais
The Brussels Times: twenty words to insult someone like a true Belgian: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · French; Source: https://www.brusselstimes.com/463760/twenty-words-that-will-help-you-insult-someone-like-a-true-belgian
lalanguefrancaise.com dictionary entries: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · French; Source: https://www.lalanguefrancaise.com
English Wiktionary: Reference only: meanings, register and region labels were checked; no text was copied (glosses, notes and examples are original). · French; Source: https://en.wiktionary.org
Charles Perrault, Le Maître Chat ou le Chat botté, in Histoires ou contes du temps passé (1697): Public domain (17th-century text) · French; Charles Perrault, Histoires ou contes du temps passé (1697)
Charles Perrault, Cendrillon ou la Petite Pantoufle de verre, in Histoires ou contes du temps passé (1697): Public domain (17th-century text) · French; Charles Perrault, Histoires ou contes du temps passé (1697)
Charles Perrault, Le Petit Poucet, in Histoires ou contes du temps passé (1697): Public domain (17th-century text) · French; Charles Perrault, Histoires ou contes du temps passé (1697)
Alphonse Daudet, La Chèvre de M. Seguin, in Lettres de mon moulin (1869): Public domain (Daudet died in 1897) · French; Alphonse Daudet, Lettres de mon moulin (1869)
Wikipedia, 'Japanese profanity': CC BY-SA 4.0 (reference only, nothing copied) · Japanese; Wikipedia contributors, 'Japanese profanity'; Source: https://en.wikipedia.org/wiki/Japanese_profanity
English Wiktionary (Japanese entries and the Japanese vulgarities category): CC BY-SA 4.0 (reference only, nothing copied) · Japanese; Wiktionary contributors; Source: https://en.wiktionary.org/wiki/ちんこ
Momotarō (the Peach Boy), Japanese folk tale: Public domain (traditional folklore; Edo-period printed versions) · Japanese; Traditional Japanese folk tale, as printed in Edo-period picture books (akahon, kusazōshi) and later retellings
Urashima Tarō, Japanese folk tale: Public domain (traditional folklore; early versions in the Nihon Shoki and Man'yōshū, the familiar plot from the Otogizōshi) · Japanese; Traditional Japanese folk tale
Kasa Jizō (the straw hats and the jizō), Japanese folk tale: Public domain (traditional folklore, told across Japan) · Japanese; Traditional Japanese folk tale
Jōyō Kanji Table (常用漢字表), Cabinet Notice No. 2 of 2010, Agency for Cultural Affairs: Government notice (list of characters and readings; facts, not copyrightable content) · Japanese; Agency for Cultural Affairs, Government of Japan: Jōyō Kanji Table (2010); Source: https://www.bunka.go.jp/kokugo_nihongo/sisaku/joho/joho/kijun/naikaku/kanji/
Tsuru no Ongaeshi (The Crane's Return of a Favor), Japanese folk tale: Public domain (traditional folklore, told across Japan) · Japanese; Traditional Japanese folk tale
Jonathan Waller's JLPT Resources: JLPT N3 kanji list (via the kanji-data JSON by David Gouveia): Creative Commons BY (tanos.co.uk); the kanji-data JSON that carries the level field is MIT (github.com/davidluzgouveia/kanji-data) · Japanese; Jonathan Waller, JLPT Resources (tanos.co.uk); David Gouveia, kanji-data; Source: http://www.tanos.co.uk/jlpt/
Issun-bōshi (The One-Inch Boy), Japanese folk tale: Public domain (traditional folklore; the Otogizōshi tales of the Muromachi and Edo periods) · Japanese; Traditional Japanese folk tale
Livy, Ab Urbe Condita, books 1, 2 and 21: Public domain (ancient text, 1st century BC/AD) · Latin; Titus Livius, Ab Urbe Condita 1.3-1.13, 2.10, 2.12-2.13 and 21.35-21.38; Source: https://www.thelatinlibrary.com/livy.html
Ovid, Metamorphoses, books 4, 8 and 11: Public domain (ancient text, 1st century BC/AD) · Latin; Publius Ovidius Naso, Metamorphoses 4.55-4.166 and 8.183-8.235 and 11.85-11.193; Source: https://www.thelatinlibrary.com/ovid/ovid.met4.shtml
Wikipedia, 'Latin obscenity' (summary of J. N. Adams' work): CC BY-SA 4.0 (reference only, nothing copied) · Latin; Wikipedia contributors, 'Latin obscenity'; Source: https://en.wikipedia.org/wiki/Latin_obscenity
J. N. Adams, The Latin Sexual Vocabulary (Johns Hopkins University Press, 1982): All rights reserved (reference only, nothing copied) · Latin; J. N. Adams; Source: https://www.press.jhu.edu/books/title/2690/latin-sexual-vocabulary
Lewis & Short, Gaffiot and Georges via lsj.gr: Public domain dictionaries (reference only) · Latin; Lewis and Short, A Latin Dictionary (1879); Gaffiot (1934); Georges; Source: https://lsj.gr/wiki/furcifer
English Wiktionary (Latin entries): CC BY-SA 4.0 (reference only, nothing copied) · Latin; Wiktionary contributors; Source: https://en.wiktionary.org/
Aulus Gellius, Noctes Atticae 11.6 (who swears by Hercules, Castor and Pollux): Public domain (ancient text); the translation page is reference only · Latin; Aulus Gellius, Noctes Atticae 11.6; Source: https://diotima-doctafemina.org/translations/latin/aulus-gellius-introduction/aulus-gellius-11-6/
Pompeian inscriptions, CIL IV (cacātor cavē malum, 7714-7716; the Lupanar, 2175 and 2275): Public domain (ancient inscriptions); photo site reference only · Latin; Corpus Inscriptionum Latinarum IV; Source: https://pompeii.pictures/R3/3%2004%2003%20p7.htm
University of Oklahoma Latin club, insult handout (Plautus-style vocatives): All rights reserved (pointer only, nothing copied) · Latin; Ludi Latini, University of Oklahoma; Source: https://www.ou.edu/ludilatini/insultshandoutFall2003.htm
Julius Caesar, Commentarii de Bello Gallico: Public domain (ancient text, 1st century BC/AD) · Latin; Gaius Iulius Caesar, De Bello Gallico 1.1, 4.17 and 4.25; Source: https://www.thelatinlibrary.com/caesar/gall1.shtml
Catullus, Carmina 1, 3, 5, 31, 85 and 101: Public domain (ancient text, 1st century BC/AD) · Latin; Gaius Valerius Catullus, Carmina 1.1, 3.1-3, 3.16, 5, 31.1-2, 85, 101; Source: https://www.thelatinlibrary.com/catullus.shtml
Martial, Epigrams 1.32, 1.38, 3.9, 5.43 and 12.46: Public domain (ancient text, 1st century BC/AD) · Latin; Marcus Valerius Martialis, Epigrammata 1.2, 1.32, 1.38, 1.52, 1.117, 3.9, 5.43, 12.46; Source: https://www.thelatinlibrary.com/martial.html
Polybius, Histories, books 3 and 15: Public domain (ancient Greek text, 2nd century BC) · Latin; Polybius, Histories 3.53 and 15.12; Source: https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Polybius/home.html
Suetonius, Life of Claudius (De Vita Caesarum 5): Public domain (ancient text, 2nd century AD) · Latin; Gaius Suetonius Tranquillus, Divus Claudius 21.6; Source: https://www.thelatinlibrary.com/suetonius/suet.claudius.html
Cicero, Cato Maior de Senectute: Public domain (ancient text, 1st century BC) · Latin; Marcus Tullius Cicero, De Senectute 7-8; Source: https://www.thelatinlibrary.com/cicero/senectute.shtml
Virgil, Aeneid book 1-2 and Eclogues 1: Public domain (ancient text, 1st century BC) · Latin; Publius Vergilius Maro, Aeneis 1.1-1.11 and 2.1; Eclogae 1.2; Source: https://www.thelatinlibrary.com/verg.html
Cicero, Pro Archia Poeta: Public domain (ancient text, 1st century BC) · Latin; Marcus Tullius Cicero, Pro Archia 24; Source: https://www.thelatinlibrary.com/cicero/arch.shtml
Henry Wadsworth Longfellow, Evangeline (1847): Public domain (published 1847) · Latin; Henry Wadsworth Longfellow, Evangeline: A Tale of Acadie, line 1; Source: https://www.gutenberg.org/ebooks/2039
Dies irae (13th-century Latin hymn): Public domain (medieval text) · Latin; Dies irae, lines 1-2; Source: https://www.thelatinlibrary.com/diesirae.html
Pliny the Younger, Epistulae, book 6: Public domain (ancient text, 1st-2nd century AD) · Latin; Gaius Plinius Caecilius Secundus, Epistulae 6.16.4-6.16.20; Source: https://www.thelatinlibrary.com/pliny.ep6.html
Cicero, Epistulae ad familiares, book 14: Public domain (ancient text, 1st century BC) · Latin; Marcus Tullius Cicero, Ad familiares 14.20; Source: https://www.thelatinlibrary.com/cicero/fam14.shtml
Horace, Carmina (Odes) and Epistles: Public domain (ancient text, 1st century BC) · Latin; Quintus Horatius Flaccus, Carmina 1.1.1, 1.9.1-2, 1.11, 1.22.1, 3.30.13-14; Epistulae 1.2.40; Source: https://www.thelatinlibrary.com/horace.html
Seneca, Epistulae morales ad Lucilium; Hercules Furens: Public domain (ancient text, 1st century AD) · Latin; Lucius Annaeus Seneca, Epistulae 1.1-1.3, 7.8, 24.20, 96.5, 106.12; Hercules Furens 437; Source: https://www.thelatinlibrary.com/sen/seneca.ep1.shtml
Tacitus, Agricola: Public domain (ancient text, AD 98) · Latin; Publius Cornelius Tacitus, De vita Iulii Agricolae 30; Source: https://www.thelatinlibrary.com/tacitus/tac.agri.shtml
Study of 27 Thai swear words (IJLHE, STKIP PGRI Bandar Lampung): Journal article, reference only (nothing copied) · Thai; International Journal of Language, Humanities, and Education; Source: https://jurnal.stkippgribl.ac.id/index.php/ijlhe/article/download/1766/1340/4554
Osaka University paper on Thai abusive language (kham-daa) by semantic field: Journal article, reference only (nothing copied) · Thai; Osaka University Knowledge Archive; Source: https://ir.library.osaka-u.ac.jp/repo/ouka/all/7809/riwl_001_185.pdf
Thai translations of English swearing (Journal of Humanities, ThaiJO): Journal article, reference only (nothing copied) · Thai; ThaiJO; Source: https://so03.tci-thaijo.org/index.php/JHUMANS/article/download/271566/184809/1179680
English Wiktionary, Category:Thai vulgarities: CC BY-SA 4.0 (reference only, nothing copied) · Thai; Wiktionary contributors; Source: https://en.wiktionary.org/wiki/Category:Thai_vulgarities
Thailand Starter Kit, 'A G-rated look at Thai sex words': All rights reserved (reference only, nothing copied) · Thai; Thailand Starter Kit; Source: https://www.thailandstarterkit.com/learn-thai/a-g-rated-look-at-thai-sex-words/
ThaiPod101 slang lessons (found by web search this session): All rights reserved (reference only, nothing copied) · Thai; ThaiPod101; Source: https://www.thaipod101.com/lesson/mustknow-thai-slang-words-phrases-5-words-describing-personalities-1
ปลาบู่ทอง (The Golden Goby), traditional Thai folk tale; plot outlines in Wikipedia, 'Pla Bu Thong', and Thailex, 'Pla Boo Thong (ปลาบู่ทอง)': Traditional tale (public domain); the outlines were used for the plot only (Wikipedia text is CC BY-SA 4.0, none copied) · Thai; Traditional Thai folk tale ปลาบู่ทอง; Source: https://en.wikipedia.org/wiki/Pla_Bu_Thong
Duddubha Jataka (Jataka no. 322, 'The Sound the Hare Heard'), told in Thailand as กระต่ายตื่นตูม: Public domain (ancient Pali text; the Cowell translation, 1897, is public domain); plot only · Thai; Jataka no. 322, Duddubha Jataka; E. B. Cowell (ed.), The Jataka, vol. 3 (1897); Source: https://www.sacred-texts.com/bud/j3/j3023.htm
Kacchapa Jataka (Jataka no. 215, 'the talkative tortoise'), told in Thailand as เต่ากับหงส์; the Panchatantra version of the same fable: Public domain (ancient text; the Rouse translation in Cowell (ed.), The Jataka, vol. 2, 1895, is public domain); plot only · Thai; Jataka no. 215, Kacchapa Jataka; E. B. Cowell (ed.), The Jataka, vol. 2 (1895); Source: https://sacred-texts.com/bud/j2/j2068.htm
The World Factbook (CIA), via the factbook/factbook.json mirror on GitHub: Public domain (a work of the US Government; the mirror's JSON conversion is public domain too); The World Factbook, Central Intelligence Agency; Source: https://github.com/factbook/factbook.json
Natural Earth (1:110m and 1:50m cultural and physical vectors): Public domain; Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com.; Source: https://www.naturalearthdata.com/
world-atlas (npm package, TopoJSON of Natural Earth admin 0 countries and land): ISC (package); the data is Natural Earth, public domain; Mike Bostock, world-atlas 2.0.2; Source: https://github.com/topojson/world-atlas
d3-geo and topojson-client (npm packages): ISC; Mike Bostock and contributors; Source: https://github.com/d3/d3-geo
UNESCO World Heritage List: Facts only (inscription status, names); no text or images used; Source: https://whc.unesco.org/en/list/
National flag descriptions (CIA World Factbook flag descriptions; national flag laws for colors and proportions where known): Flags of states are not subject to copyright as designs; descriptions are public domain (US Government work); Source: https://github.com/factbook/factbook.json
Standard reference facts (encyclopedias, national geographic agencies), written from general knowledge: Facts only; every sentence written for this project
Encyclopaedia Britannica (river lengths, lake areas, heights): Facts only (numbers); no text used; Source: https://www.britannica.com/
U.S. Geological Survey, lengths of the major rivers of the United States: Public domain (a work of the US Government); facts only; Source: https://www.usgs.gov/
FAO news release 'Lake Chad facing humanitarian disaster' (2009): the lake shrank by about 90% from 1963 to 2001: Facts only; no text used; Source: https://www.fao.org/newsroom/detail/Lake-Chad-facing-humanitarian-disaster/