audio.cpp Model Licenses and Commercial Use
Written in September 2026. License terms change between versions, so everything below reflects the situation at that time. Always check the project's current LICENSE text before making a commercial decision.
Read this first (important disclaimer) There are a lot of models available for download here, and we recommend using them for learning and research only. We only provide the software installation service. This document makes no guarantee about the accuracy of any model's license. If you plan to use a model commercially, verify the license terms yourself through an authoritative source (the model's official repository, the original author's website or contact details) before you use it. The classifications and conclusions below come from our own reading of publicly available information at the time of writing, and may change as upstream projects update. A model marked "to be confirmed" simply means we have not verified it yet — we will keep filling these in.
The two projects covered here
audio.cpp
Repository: https://github.com/0xShug0/audio.cpp
A local audio processing tool that runs a range of audio features on your own machine, including text-to-speech, speech recognition, voice conversion, and vocal/accompaniment separation. It is written in C++ and uses quantization to optimize the models (in short: compressing them to make them lighter), so it runs considerably faster than the official apps and uses less RAM and VRAM — even a mid-spec computer runs it smoothly. That compression can very occasionally cost a little output quality, but for most users the results are perfectly acceptable. It supports a wide range of computers and GPUs, and it runs entirely locally with no internet connection required, so your privacy is protected.
audio.cpp-webui
Repository: https://github.com/kigner/audio.cpp-webui
audio.cpp-webui builds on the audio.cpp project and adds a friendly graphical interface. Instead of typing commands, you use everything through a web page — upload audio, type your text, pick your parameters, and generate the result in one click. This version pays particular attention to the Windows experience: it ships with a one-click launch script, so you just download it and double-click. It makes those fast, lightweight local AI audio capabilities easy for non-technical users too.
Understand this first: the software license ≠ the model license (the key point)
When you use audio.cpp / audio.cpp-webui, you are actually bound by two independent sets of licensing terms. Almost every commercial-use risk comes from confusing the two.
| Layer | What it is | Licensing |
|---|---|---|
| ① The software itself | The source code and executables of audio.cpp and audio.cpp-webui | Apache-2.0 — permissive open source; free to use, modify, and commercialize |
| ② The model weights | The TTS, ASR, voice conversion, and music generation models you download and load inside the software | Varies model by model — anywhere from "free for commercial use" to "commercial use prohibited"; each one must be checked (see the classifications below) |
The software being Apache-2.0 does not mean the models you load with it — or the content you generate — are free to commercialize. What determines your commercial risk is always layer ②: the license of the model itself.
Three things to watch out for:
- Quantization does not change the license. audio.cpp loads quantized, compressed model files (smaller and faster). Quantization only converts the numerical precision of the original weights — the result is a derivative work of the original model, and the original license terms continue to apply unchanged. "I'm not using the official original, I'm using a compressed version" is not a way around the license.
- Rights to the inference output are a separate question. Some model licenses restrict not only whether you may use the model, but also whether you may commercially use the content it generates. If your business output is the audio itself (voiceover, audiobooks, music, and so on), read the license text closely on this point.
- Bundled sub-components are covered too. Running a model often also loads separate tokenizers, text encoders, vocoders, and similar components. These may come from different projects under different licenses — verify them as well before commercial use.
A simple way to stay out of trouble: if you're just experimenting locally, learning, or doing research, use whatever you like. The moment any commercial purpose is involved (charging customers, internal business use, monetized content, deliverables for a client, etc.), pick only from section "1. ✅ Free for commercial use" below and keep the required attributions. For models under "⚠️ Conditional commercial use", read the full license text clause by clause before deciding. For anything under "❌ Commercial use prohibited" or "❓ To be confirmed", do not use it commercially at all until you have verified it.
Legend
| Marker | Meaning |
|---|---|
| ✅ Free for commercial use | Permissive license; generally no fee and no extra conditions for commercial use |
| ⚠️ Conditional commercial use | Usually free for commercial use, but subject to conditions (revenue/scale caps, attribution, copyleft, registration, etc.) — read the original license first |
| ❌ Commercial use prohibited | Research / non-commercial use only; commercial use is not permitted |
| ❓ To be confirmed | We have not been able to verify the license yet. This does not mean it is commercial-friendly — confirm it yourself before use |
1. ✅ Free for commercial use (prefer these)
Text-to-speech (TTS)
| Model | License | Notes |
|---|---|---|
| Chatterbox | MIT | Permissive open source; free to use and commercialize |
| GLM-TTS | MIT | Permissive open source; free to use and commercialize |
| VibeVoice | MIT | Microsoft long-form multi-speaker TTS |
| Confucius4-TTS | Apache-2.0 | Permissive open source; free to use and commercialize |
| DotTTS | Apache-2.0 | Permissive open source; free to use and commercialize |
| MOSS-TTS-Local | Apache-2.0 | MOSS flagship TTS |
| MOSS-TTS-Nano | Apache-2.0 | MOSS lightweight realtime TTS |
| Qwen3-TTS | Apache-2.0 | Permissive open source; free to use and commercialize |
| VoxCPM2 | Apache-2.0 | OpenBMB tokenizer-free TTS |
| PocketTTS | CC-BY-4.0 | Commercial use allowed, attribution required per CC-BY |
Speech recognition (ASR)
| Model | License | Notes |
|---|---|---|
| Qwen3-ASR | Apache-2.0 | Permissive open source; free to use and commercialize |
| SenseVoice-Small | Apache-2.0 | Multilingual speech recognition, speech emotion recognition, and audio event detection |
| VibeVoice ASR | MIT | Microsoft long-form speech transcription |
| Parakeet-TDT 0.6B v3 | CC-BY-4.0 | Commercial use allowed, attribution required per CC-BY |
Speech analysis (forced alignment / speaker)
| Model | License | Notes |
|---|---|---|
| Qwen3 Forced Aligner | Apache-2.0 | Audio-to-text forced alignment |
Audio / music generation
| Model | License | Notes |
|---|---|---|
| ACE-Step (1.5) | MIT | Music generation; note that ACE-Step v1-3.5B is the Apache-2.0 release — what this project bundles is 1.5 (MIT) |
| HeartMuLa | Apache-2.0 | Music generation (HeartMuLa-oss-3B + HeartCodec) |
2. ⚠️ Conditional commercial use (you must read the specific license terms)
The models below may allow free commercial use once certain conditions are met, but every vendor's terms differ. Check the original license clause by clause before any commercial use. What follows lists only the license name and the typical restrictions — it is not a substitute for the original text.
| Model | Category | License name | Typical conditions (the original text governs) |
|---|---|---|---|
| IndexTTS2 | TTS | bilibili Model Use License | Bilibili's custom model license; typically includes restrictions on scope of use, attribution, etc. |
| DramaBox | TTS | LTX-2 Community License (Lightricks) | Community license; usually permits free commercial use subject to revenue/scale caps and similar conditions |
| Fun-ASR-Nano | ASR | FunASR Model Open Source License Agreement v1.1 | Custom license; often free for commercial use but with scale/revenue/attribution limits and a ban on reselling the weights |
| Nemotron 3.5 ASR | ASR | NVIDIA custom license (listed as "other" on HF) | Non-standard open source agreement; usually permits commercial use with usage restrictions, notice-retention terms, etc. |
| Seed-VC | Voice conversion | GPL-3.0 | Commercial use allowed, but copyleft is viral — distributing derivative works requires releasing them under the GPL. Have legal review it before integrating into a closed-source product |
| Stable Audio 3 | Audio generation | Stability AI Community License (stable-audio-community) | Free for research/non-commercial use; commercial use requires annual revenue under US$1M plus registration at stability.ai; at US$1M or above you must purchase an Enterprise License; may not be used to train a competing foundation model |
| MiniMax-H3 | Audio generation | MiniMax H3 Community License Agreement | Community license; generally allows limited commercial use subject to revenue/scale conditions — read the MiniMax license text for specifics |
3. ❌ Commercial use prohibited (research / non-commercial only)
| Model | Category | License | Notes |
|---|---|---|---|
| Hviske ASR | ASR | CC-BY-NC-4.0 | Non-commercial license; commercial use prohibited |
| OmniVoice | TTS | CC-BY-NC-4.0 | Non-commercial license; commercial use prohibited |
| Sortformer Diarization | Speech analysis | CC-BY-NC-4.0 | Non-commercial license; commercial use prohibited |
| Fish Audio S2 Pro | TTS | fish-audio-research-license | Research-use license; commercial use prohibited |
4. ❓ License to be confirmed
We have not been able to verify the licenses of the models below, so they are grouped here as unconfirmed. This is only a temporary state — we will keep completing this document. Until a license is verified, do not assume it is commercial-friendly; if you need to use one, confirm it yourself with the upstream repository or the original author.
Text-to-speech (TTS)
Higgs Audio v3 TTS, Inflect Micro v2, Irodori-TTS, MioTTS, NeuTTS, Llama-OuteTTS 1.0, Supertonic 3, VieNeu-TTS v3 Turbo
Speech recognition (ASR)
Citrinet ASR, Higgs Audio v3 STT, Kroko Community ASR, Voxtral Mini 4B Realtime
Voice conversion
RVC, Vevo2
Audio processing tools (separation / codec / score)
BS-RoFormer, HTDemucs, Mel-Band RoFormer, MioCodec, MuScriptor
One more reminder: the audio.cpp / audio.cpp-webui software itself is Apache-2.0, but that grants you no rights over any model. Always follow the "software license ≠ model license" reasoning above and check the license of every model you actually load, along with its bundled sub-components. There are many models available for download here and we recommend using them for learning and research only; we provide the installation service alone and make no guarantee about the accuracy of any model's license. For commercial use, verify through an authoritative source such as the model's official repository or the original author's website, or contact the original developer directly.