# Third-Party Components

## Core (always)

| Component | License | Notes |
|---|---|---|
| PySide6 (Qt for Python) | LGPL v3 / GPL | GUI toolkit |
| numpy, scipy, soundfile | BSD / BSD-3 / 3-clause BSD | audio math & IO |
| noisereduce | Unlicense / MIT (see repo) | DSP voice isolation ("fast" mode) |
| ffmpeg / ffprobe | LGPL v2.1+ (GPL builds exist) | media I/O; bundled binary must match license |

## Optional — AI voice separation (only if the user installs `requirements-ai.txt`)

| Component | License | Notes |
|---|---|---|
| demucs 4.1.x (Meta/Facebook) | Code: MIT | source separation engine |
| PyTorch (torch 2.x) | BSD-3 | deep-learning runtime |
| htdemucs_ft weights (~90 MB) | **MIT** (per the model card of `adefossez/HTDemucs-ft` on Hugging Face) | downloaded on first use from Hugging Face, cached in the user data dir — never bundled |
| huggingface_hub | Apache-2.0 | model download plumbing |

### License gate (project policy)

We only use checkpoints whose license we can point to. Demucs code = MIT,
`htdemucs_ft` weights = MIT (model card). They are only ever *downloaded by*
the *user* on first use — never bundled by us. RoFormer / UVR community
checkpoints have mixed or research-only licensing and are therefore **not**
used.