# Felucca licensing Felucca is free software. Its **code** is licensed under the GNU General Public License, version 3 only (`GPL-3.0-only`, full text in `LICENSE`). Its **assets** are not part of that licence: the icon atlas `assets/icons.png`, the panel image `docs/panel.jpg` and the drum sounds made by `tools/gen_waves.py` (the Hügelton Sample Pack) are Copyright (C) 2026 Hügelton Instruments, all rights reserved. Their licence terms will be published later. SLOOP's firmware does not contain the Hügelton Sample Pack: its sampled drum kit is made of CC0 recordings (`assets/samples-cc0/KIT`), and `gen_waves.py` only feeds the SLICE engine's demo loop, which SLOOP does not build. Copyright (C) 2026 Leo Kuroshita (@kurogedelic), Hügelton Instruments ## What is code (GPL-3.0-only) Every file in this tree that carries an `SPDX-License-Identifier: GPL-3.0-only` header (one source file carries another: `firmware/src/fm6_core.c`, msfa, Apache-2.0, below; the firmware built with it is GPL-3.0-only as a whole): - the firmware: `firmware/` (app, HAL, update loader) - the build script and tools: `build.sh`, `tools/` - the web pages (installer, editor) and their tests: `web/` (not the Fukiai font, below) - the SLOOP plugin for tuttidaw: `web/plugin/` (below) - the host tests: `tests/` You may use, study, change and share it under the GPL. If you distribute Felucca, 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 Felucca inside. ## Additional permission (GPL-3.0 section 7) As an additional permission under GPL-3.0 section 7, you may combine Felucca, or a work based on it, with the Felucca Assets (above), and convey the combination. This is allowed even though the Felucca Assets are not licensed under the GPL, provided that: - you follow the GPL for every part that is not a Felucca Asset; and - you follow the terms published for the assets. The Felucca Assets are data (wavetables, icons, sample data). They are not program code. A firmware image built from the GPL sources with replacement assets, or with no assets, is entirely governed by the GPL. ## Third-party material | What | Licence | Where | | --- | --- | --- | | Instrument and drum samples (Versilian Studios VSCO-2 CE, VCSL; Sonic Pi: SCRCH) | CC0 1.0 | `assets/samples-cc0/`, provenance in `ATTRIBUTION.txt` there | | Terminus font 8x16: the FM-1's screen (Terminus Bold, ter-u16b, SLOOP 2.6), and the web editor's font (the regular ter-u16n; `tools/gen_webfont.py` makes it a TrueType font inlined in `web/editor.html`) | SIL OFL 1.1 | `assets/fonts/ter-u16b.bdf`, `assets/fonts/ter-u16n.bdf`, `assets/fonts/Terminus-LICENSE.txt` | | Fukiai icon font (Hügelton Instruments), web editor only | MIT | `web/fukiai.ttf`, `web/FUKIAI-LICENSE.txt` | | CrispyZebra by Leo Kuroshita (): the PHASE engine's waveforms are a C port of its oscillator | GPL-3.0 | `firmware/src/eng_phase.c` | | klattsch by Tony Gies (): design reference for the VOICE (formant) engine; no code copied. Formant data from Klatt (1980) / Hillenbrand et al. (1995) | MIT (klattsch) | credit only | | msfa by Google Inc. and Pascal Gauthier, from Dexed (): the FM6 engine's synthesis (SLOOP 2.4), ported to integer C for Felucca 1.0 by Leo Kuroshita (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` | | DaisySP (Electrosmith, Emilie Gillet) and Rings' sympathetic strings (Emilie Gillet): the PHYS engine's models (SLOOP 2.5, from Felucca 1.0, ported to fixed point by Leo Kuroshita) | MIT | `firmware/src/phys_dsp.c`, `firmware/src/phys_symp.c` (the notice is in each file) | | JieLi AC79 SDK: `uboot.boot`, `cfg_tool.bin`, `eq_cfg_hw.bin` are read from your SDK checkout at build time and placed in the package; no SDK files are in this tree | Apache-2.0 | | ## The SLOOP plugin for tuttidaw (weavejam) `web/plugin/` (the whole firmware as a device in the browser, the headless renderer, the stems, the fractional tempo, the editor on that device, the plugin protocol, the site's build) and the `SLOOP_TUTTI` parts of the firmware it needs are by weavejam, in the fork , under GPL-3.0-only like the rest of SLOOP: Copyright (C) 2026 weavejam It is weavejam's plugin build of SLOOP by isod89 (): all of its sound, its sequencer and its editor are SLOOP's, and everything above and below applies to it. It is built without the Felucca Assets that are not under the GPL (the icon atlas: `FELUCCA_ICONS=0`, the plugin has no screen; SLOOP has no Hügelton Sample Pack). Its site (`web/plugin/build.sh`) serves the licence texts, this file and the samples' attribution with it (`/licenses/`), names its source (the commit it was built from) on `/credits.html`, and says that it is not affiliated with or endorsed by M-VAVE or Hügelton Instruments. tuttidaw only talks to it at arm's length (a sandboxed frame of another site, messages): tuttidaw is not part of it and does not become GPL by hosting it. ## Contributions Contributions are welcome under GPL-3.0-only. By submitting one, you agree that it may be combined with the Felucca Assets under the section 7 permission above. ## Trademarks "Felucca" and "Hügelton Instruments" are names of Hügelton Instruments. "M-VAVE" and "FM-1" are trademarks of their respective owners. Felucca is independent firmware that runs on FM-1 hardware. It is not affiliated with, endorsed by or supported by those owners. ## Radio Felucca never enables the Bluetooth / Wi-Fi radio of the hardware.