License¶
In a nutshell
OVOS follows a universal donor licensing policy: the code should be usable by anyone,
anywhere, with no strings attached. In practice that means permissive licenses, mostly
Apache 2.0 or BSD, for all core components, with a short, explicitly documented list of
exceptions. Each exception is either a dependency forcing a stricter license on one
specific plugin, or a plugin repository that never shipped a LICENSE file at all.
Under the universal donor policy, OVOS code should be usable anywhere by anyone, with no conditions attached. OVOS is predominantly Apache 2.0 or BSD licensed. The exceptions are a small minority of plugins, and every one of them is listed in the table below. Each exception exists either because a dependency forces a stricter license, or because the plugin's own repository never shipped a LICENSE file at all.
Individual plugins or skills may carry their own license when they wrap a dependency that requires it. For example, a TTS plugin that wraps an AGPL-licensed engine cannot itself be relicensed under a more permissive term. Core components are kept fully free. Any code whose license cannot be controlled lives in an optional plugin instead, flagged as such.
This also means avoiding LGPL code, for the reasons explained in this discussion of the GPL classpath exception.
Padatious used to be listed here. It was ported from libfann to pure numpy, so it is Apache-2.0 with no reservations and is no longer an exception.
Policy properties¶
The license policy has the following properties:
- It gives the user of the software complete and unrestrained access, so they may
inspect, modify, and redistribute their changes:
- Inspection: anyone may inspect the software for security vulnerabilities.
- Modification: anyone may modify the software to fix issues or add features.
- Redistribution: anyone may redistribute the software on their own terms.
- It is compatible with GPL licenses. Projects licensed as GPL can be distributed with OVOS.
- It allows incorporating GPL-incompatible free software, such as CDDL-licensed code.
The policy does not restrict what software may run on OVOS. Thanks to the plugin architecture, even traditionally tightly-coupled components such as drivers can be distributed separately, so plugin maintainers are free to choose whatever license fits their own project.
Notable licensing exceptions¶
The repositories below do not follow the universal donor policy. Check their licenses are compatible with your use case before depending on them.
| Repository | License | Reason |
|---|---|---|
| ovos-tts-plugin-mimic3 | AGPL | depends on mimic3 (AGPL-3.0). This plugin is archived. See Deprecated & Archived Repositories for the current replacement |
| ovos-tts-plugin-espeakNG | GPL | depends on espeak-ng (GPL-3.0) |
| ovos-tts-plugin-SAM | see repo (no license file) | the package self-declares Apache-2.0 in its pyproject.toml. The repository ships no LICENSE file. The underlying S.A.M. engine is reverse-engineered abandonware with no clear upstream license |
| ovos-tts-plugin-phoonnx (built into phoonnx) | Apache-2.0 (code); models per model card | the phoonnx repository gained an Apache-2.0 LICENSE in 2026; individual voices still carry their own model-card terms. See the TTS plugin table |
| ovos-tts-plugin-beepspeak | no license file | novelty R2-D2-style TTS plugin. The repository ships no LICENSE file |
| ovos-tts-plugin-lux | see repo (no license file) | zipvoice-based voice-cloning TTS plugin. The package self-declares Apache-2.0 in its setup.py (with the OSI Apache classifier), but the repository ships no standalone LICENSE file |
| ovos-stt-plugin-HiTZ | no license file | archived/deprecated Basque STT plugin. The repository ships no LICENSE file |
| ovos-lang-detector-classics-plugin | see repo (no license file) | heuristic language-detector plugin. The pyproject.toml declares Apache-2.0, but the repository ships no LICENSE file |
| kw-template-matcher | see repo (no license file) | template-matching library + opm.transformer.intent plugin. The setup.py classifier says MIT, but the repository ships no LICENSE file |
The rows above with no license file are not a rejection of the universal donor policy. They are repositories that never declared one, so no license can be assumed for redistribution purposes. Treat "no license file" as more restrictive than any permissive license, not less.
See also: Why OpenVoiceOS Uses Permissive Licenses (OVOS blog).
Read next: Reference Overview Related: Deprecated & Archived Repositories · OVOS Repository Index · Contributing