OFFLINE AI NPCThe espeak boundary
Piper is an optional external process. Its archived engine source is MIT, while its phonemizer links GPL-3.0 espeak-ng. A top-level MIT label does not cover the whole native distribution, its dictionaries, ONNX Runtime's notices or voice models.
The current package boundary
The plugin invokes Piper over stdin/stdout JSON, does not load its libraries into Unity, and can operate with another engine or typed input. Piper, espeak, their data and voice weights are installed outside Assets/OfflineAINPC/. The export preflight excludes native/model payloads and espeak data from that folder. This is a source/export rule; review the actual release package and game distribution separately.
The GNU aggregation FAQ considers both the communication mechanism and its semantics. Separate processes and pipes support the documented boundary, but they are not an unconditional legal guarantee for every future integration. Distribution location alone also does not settle whether programs form one work. Keep the boundary and re-review changes that alter it.
If distributing the Piper stack
| Artifact | What must be identified |
|---|---|
| Piper executable and piper-phonemize | Exact source revisions, patches, build/install scripts and dependencies. |
| espeak-ng library | GPL-covered source matching the actual binary, including the fork revision. |
| espeak-ng-data | Exact dictionary sources, generated data and build inputs; individual notices where applicable. |
| ONNX Runtime and other libraries | Actual versions, licence/copyright texts and ThirdPartyNotices. |
| Voice weights / libtashkeel model | Their independent weight, dataset and fine-tune provenance. |
GPL-covered object-code distribution requires a method allowed by GPL-3.0 sections 1 and 6, licence/notices and no additional restrictions on the covered components. For section 6(d), equivalent no-charge Corresponding Source access and clear directions accompany the binary offering. Other section 6 methods have their own conditions. A generic upstream URL or written offer is not automatic compliance.
Archived Piper's 2023.11.14-2 CMake can fetch a moving phonemizer branch. Its tag alone therefore does not identify the entire installed stack's Corresponding Source. A version string is supporting evidence, not a substitute for matching the binaries and dictionary files you ship to their source.
The current process boundary is designed to keep the plugin separate. Do not infer that every proprietary game, modified protocol or combined distribution is automatically cleared. The actual combination and redistribution conditions need their own review.
Voices, phoneme routes and output
Voice files are a separate question: the dataset licence, fine-tune base and independent weight terms need review. A Chinese pinyin route or an unused espeak backend does not remove GPL-covered files that are still present in a distributed Piper folder.
The GNU output FAQ generally distinguishes output from copyright in program code, with exceptions where protected content is copied. Independent recording, voice, model and other rights still apply. The process boundary does not establish that all generated audio owes no obligations.
When to review again
- When changing process/library integration or the communication protocol.
- When adding an engine installer, changing its destination or exporting the package.
- Before distributing an engine, native library, dictionary or model with a game.
- When selecting a different Piper fork, phonemizer, voice or preprocessing model.
Existing working Piper configurations remain supported. A new engine choice needs its own exact inventory; this document does not grant blanket clearance to Qwen3-TTS or any other alternative. See THIRD_PARTY_NOTICES.md.