ZenTrain Studio

LICENSES AND CREDITS

Licenses and credits

Last updated 25 October 2026. ZenTrain Studio is built with the open-source parts below. We thank their authors. Each part is licensed to you under its own licence, whose full text comes with the app (About, Licenses and credits, under Licence texts); nothing in our Terms of use limits the rights those licences give you. These parts come with no warranty from their authors, as their licences say.

The voice

  • Kokoro-82M v1.0 neural voice model and voices, by hexgrad: Apache License 2.0 (huggingface.co/hexgrad/Kokoro-82M).
  • ONNX Runtime 1.30.0, by Microsoft, which runs the voice on the phone: MIT License, with its own third-party notices. Its usage reporting (telemetry) is switched off in the app.
  • How words are pronounced is the app's own work, built on: misaki's US and British pronunciation dictionaries and its rules for small words, by hexgrad (Apache License 2.0), as converted by the sherpa-onnx project (k2-fsa, Apache License 2.0); the CMU Pronouncing Dictionary for names (BSD 2-clause licence, © 1993-2015 Carnegie Mellon University); and g2p_en's letters-to-sounds model for words no dictionary has, by Kyubyong Park and Jongseok Kim (Apache License 2.0).

The app

  • lamejs 1.2.1, the MP3 encoder for downloads, a JavaScript port of LAME (lame.sourceforge.net): GNU Lesser General Public License v3 (github.com/zhuker/lamejs). It is a separate, unmodified file in the app (lame.min.js).
  • lz-string 1.5.0 (share links): MIT License, © 2013 pieroxy.
  • QRCode.js 1.0.0 (share QR codes): MIT License, © 2012 davidshimjs.
  • Capacitor 6.2.2, the app framework, by Ionic: MIT License, © 2017-present Drifty Co.; with Apache Cordova 10.1.1 (Apache License 2.0; this product includes software developed at The Apache Software Foundation).
  • AndroidX, Kotlin and Credential Manager libraries: Apache License 2.0. Google's sign-in libraries (Google Identity Services, Google Play services): © Google LLC, under Google's terms.

Words and music

  • The words the app does not allow in names and spoken cues are adapted from the List of Dirty, Naughty, Obscene, and Otherwise Bad Words by Shutterstock: CC BY 4.0 (github.com/LDNOOBW/List-of-Dirty-Naughty-Obscene-and-Otherwise-Bad-Words).
  • The official session with Pachelbel's Canon follows the Mutopia Project edition by Michael Fischer v. Mollard (Mutopia-2015/09/02-2047): CC BY 4.0, adapted (mutopiaproject.org). The other melodies (Ode to Joy, Brahms' Lullaby, Water of Tyne, Greensleeves) follow public-domain Mutopia editions.
  • The official session Four Seasons Techno follows the Mutopia Project editions of Vivaldi's Four Seasons (Op. 8 Nos. 1-4; Mutopia-2010/02/08-301, -336, -350 and -351), typeset anonymously from Performers' Facsimiles: CC BY-SA 3.0, adapted into a dance arrangement (mutopiaproject.org; creativecommons.org/licenses/by-sa/3.0). That session is shared under the same licence.

Every sound in the app (tones, instruments, noise, the choir and the nature sounds) is synthesized by ZenTrain Studio's own sound engine as you listen: the app plays no recordings.