Usovo runs speech-synthesis models locally on your device. Some of these are built on open-source models made available by their respective creators under permissive licenses. This page lists them, as required by those licenses — for the branding and marketing story behind Usovo's own model family, see usovo.in or the in-app model cards.
None of these licenses require payment, impose usage restrictions on Usovo, or affect your rights as a Usovo user — they're reproduced here for transparency and legal completeness.
Lite
Built on Kokoro-82M by hexgrad.
License: Apache License, Version 2.0
License text: apache.org/licenses/LICENSE-2.0
A small portion of Kokoro-82M's training data (under 12 hours total, out of several hundred) was drawn from the Koniwa dataset (CC BY 3.0) and the SIWIS dataset (CC BY 4.0). These are Creative Commons attributions from the model's own training process, reproduced here for completeness.
Spinto
Built on Qwen3-TTS-12Hz-0.6B-Base by Alibaba's Qwen team.
License: Apache License, Version 2.0
License text: apache.org/licenses/LICENSE-2.0
Character-voice attribution (audiobook narration)
Usovo's audiobook feature uses Qwen3-4B-Instruct-2507 by Alibaba's Qwen team internally to detect chapter structure and attribute dialogue to characters. This runs locally on your device and is never exposed as a selectable voice model.
License: Apache License, Version 2.0
License text: apache.org/licenses/LICENSE-2.0
Apache License 2.0 — summary
Each of the above is licensed under the Apache License, Version 2.0, a permissive open-source license that allows commercial use, modification, and redistribution. It requires only that the original copyright notice and license text be preserved and made available — as this page does — and that any changes made to the licensed material be noted. It does not require Usovo to open-source its own code, and it grants no trademark rights to the licensor's name or logo.
Runtime & tooling
Usovo's on-device inference runs on MLX, Apple's open-source array framework for Apple Silicon (Apache License, Version 2.0), via community-maintained MLX conversions of the models above.
This page will be updated as models are added, removed, or changed. If a future model ships under different license terms, that will be reflected here before release.