# Skiff licensing Skiff is free software, licensed under the GNU General Public License, version 3 only (`GPL-3.0-only`, full text in `LICENSE`). That covers the code and its own assets. A few bundled or ported parts keep their own licences; they are listed below, and their licence texts are in `LICENSES/`. Skiff is a fork of Felucca 1.1.5 by Hügelton Instruments (), under the same licence. Felucca's files keep their copyright notices; Skiff's changes are marked (Skiff) in the sources. Copyright (C) 2026 Leo Kuroshita (@kurogedelic), Hügelton Instruments (Felucca) Copyright (C) 2026 illuminus5 (Skiff's changes and additions) ## What is GPL-3.0-only Every file in this tree that carries an `SPDX-License-Identifier: GPL-3.0-only` header: - the firmware: `firmware/` (app, HAL, update loader) - the build script and tools: `build.sh`, `tools/` - the web pages (installer, editor, the browser emulator `web/emu/`) and their tests: `web/` (not the Fukiai and DotGothic16 fonts, below) - the host tests: `tests/` Three source files are ports and keep the licence of their originals: `firmware/src/phys_dsp.c` (DaisySP, MIT), `firmware/src/phys_symp.c` (Rings, MIT) and `firmware/src/fm6_core.c` (msfa, Apache-2.0). The firmware built with them is GPL-3.0-only as a whole. You may use, study, change and share Skiff under the GPL. If you distribute Skiff, or firmware derived from it, you must also give your recipients its complete corresponding source under the same licence. That includes devices that ship with modified Skiff inside. ## Hügelton Instruments' own work All by Hügelton Instruments (Leo Kuroshita), in this tree: | What | Licence | Where | | --- | --- | --- | | Felucca: firmware, tools, web pages, tests | GPL-3.0-only | `LICENSE` | | The PHASE engine's waveforms: a C port of the oscillator of CrispyZebra () | GPL-3.0 | `firmware/src/eng_phase.c` | | The DRUM voices and kit | GPL-3.0-only | `firmware/src/drum_voice.c`, `firmware/src/eng_drum.c` | | The Hügelton Sample Pack: Felucca's drum sounds, made by `tools/gen_waves.py`, from which the SLICE engine's BREAK is built (not CC0) | GPL-3.0-only | `tools/gen_waves.py` | | The Fukiai icon font (): the firmware's icons (rasterised at build time by `tools/gen_aa_icons.py`) and the web editor's | MIT | `web/fukiai.ttf`, `LICENSES/MIT-Fukiai.txt`, `web/FUKIAI-LICENSE.txt` | Skiff's changes to Felucca, marked (Skiff) in the sources, and its pictures (`docs/skiff.png` from the firmware's screen renders, `docs/controls.jpg` and `docs/keystrip.pdf` drawn by `tools/gen_panel_diagram.py`) are GPL-3.0-only too. ## Third-party material | What | Licence | Where | | --- | --- | --- | | Barlow Condensed font (Medium, Bold) by The Barlow Project Authors (): Skiff's UI text, rasterised into the firmware at build time (`tools/gen_aa_font.py --preset barlow-condensed`; the generated tables are not offered as a font, and the font declares no Reserved Font Name); (Skiff 1.0) also the web editor's headings, labels and values, served with it from `web/fonts/` (its OFL text beside it) | SIL OFL 1.1 | `assets/fonts/BarlowCondensed-Medium.ttf`, `assets/fonts/BarlowCondensed-Bold.ttf`, `web/fonts/`, `LICENSES/OFL-BarlowCondensed.txt` | | Inter Tight font by The Inter Project Authors: Felucca's UI text (the `inter-tight` preset, kept in the tree) | SIL OFL 1.1 | `assets/fonts/InterTight[wght].ttf`, `LICENSES/OFL-InterTight.txt` (also `assets/fonts/OFL.txt`) | | Instrument samples (Versilian Studios VSCO-2 Community Edition, VCSL): the SAMPLE sets, also the SLICE engine's PIANO (the PIANO set's middle C) | CC0 1.0 | `assets/samples-cc0/`, provenance in `ATTRIBUTION.txt` there | | DaisySP by Electrosmith, Corp and Emilie Gillet (): the PHYS engine's modal and string models and the resonator, ported to fixed point | MIT | `firmware/src/phys_dsp.c`, `LICENSES/MIT-DaisySP.txt` | | Rings by Emilie Gillet (): the PHYS engine's sympathetic strings, ported to fixed point | MIT | `firmware/src/phys_symp.c`, `LICENSES/MIT-Rings.txt` | | msfa by Google Inc. and Pascal Gauthier, from Dexed (): the FM6 engine's synthesis, ported to integer C (Dexed itself is GPL-3.0; only msfa is used; the FM6 factory patches are Felucca's own) | Apache-2.0 | `firmware/src/fm6_core.c`, `LICENSES/Apache-2.0-msfa.txt` | | JIANT FM by juanjiant-bit (), a Felucca fork: the DRUM-X engine (its voice and factory kit as written; its engine wrapper, kit pages and test adapted to Skiff, modified 2026-10-10). DRUM-X follows the idea of Sonic Charge's Microtonic; no Microtonic code is involved | GPL-3.0-only | `firmware/src/drumx_voice.c`, `firmware/src/eng_drumx.c`, `firmware/src/ui_dx.c`, `tests/drumx_test.c` | | klattsch by Tony Gies (): design reference for the VOICE engine; no code copied. Formant data from Klatt (1980) / Hillenbrand et al. (1995) | MIT (klattsch) | credit only | | X0X by charlesvestal (), a Felucca fork: the design of the browser emulator (the worklet, the device clock driven by its audio, the exports); its files credit it in their headers | GPL-3.0 | `web/emu/` | | DotGothic16 font by The DotGothic16 Project Authors (): the browser emulator's knob labels, served with its page (cut to printable ASCII; the font declares no Reserved Font Name) | SIL OFL 1.1 | `web/emu/fonts/DotGothic16-subset.woff`, `LICENSES/OFL-DotGothic16.txt` (also `web/emu/fonts/OFL.txt`) | | JieLi AC79 SDK by JieLi Technology: three of its files go into every `.fwsc` package (below); none are in this tree | Apache-2.0 | `LICENSES/Apache-2.0.txt` | On the device, HOME held > ABOUT opens the information screen; turning PRESETS scrolls on into CREDITS, a short list of these authors, licences and source URLs. ## JieLi SDK files in the packages (Apache-2.0) A `.fwsc` package made by `tools/build.py` (with `tools/fm1pkg_make.py`; this is the package the web installer installs) holds three unmodified files from the JieLi AC79 SDK (, `cpu/wl82/tools/`). They are read from your SDK checkout at build time (see BUILDING.md); no SDK files are in this tree. | File in the package | What it is | | --- | --- | | `uboot.boot` | the first-stage boot loader (SPL) | | `cfg_tool.bin` | the chip configuration block | | `eq_cfg_hw.bin` | the default hardware EQ table | They are licensed under the Apache License, Version 2.0 (`LICENSES/Apache-2.0.txt`), not under the GPL, and their copyright stays with JieLi Technology. The SDK has no NOTICE file. Apache-2.0 files may be distributed together with GPL-3.0 code; Skiff itself stays GPL-3.0-only. Every distribution of a package carries the licence texts with it: the release folder (`tools/build.py --release`) and the site (`web/make_site.py`, next to the package in `firmware/` and linked from the installer page). ## No vendor material No M-VAVE material is part of Skiff. The firmware links no vendor code and contains no vendor data, and the packages hold only Skiff and the three SDK files above. The installer's "Return to official V15" holds only the official file's size and SHA-256: you select the official firmware file you downloaded yourself, and it is checked and installed in your browser, never uploaded or redistributed. ## Contributions Contributions are welcome under GPL-3.0-only. ## Trademarks "Felucca" and "Hügelton Instruments" are names of Hügelton Instruments. Skiff is not Felucca, and is not made, endorsed or supported by Hügelton Instruments. "M-VAVE" and "FM-1" are trademarks of their respective owners. Skiff is independent firmware that runs on FM-1 hardware. It is not affiliated with, endorsed by or supported by those owners. ## Radio Skiff never enables the Bluetooth / Wi-Fi radio of the hardware.