Gökyüzü — Copyright 2026 Mehmet Eren Dikmen Gökyüzü is a free flight simulator for the browser, created by Mehmet Eren Dikmen (https://github.com/erendikmenn) and developed with the Gökyüzü contributors. Source: https://github.com/erendikmenn/gokyuzu Code: Apache-2.0 · Asset pack (visuals and sounds): CC BY-NC 4.0, trademark-free. The code in this repository is licensed under the Apache License, Version 2.0 (see LICENSE). The files listed in section 3 below are under other licences. The game assets (3D models, textures, sounds, map tiles) are published separately, as a trademark-free asset pack on GitHub Releases, under CC BY-NC 4.0 (see ASSETS-LICENSE.md). 1. Attribution -------------- This product includes software and content created by Mehmet Eren Dikmen for Gökyüzü (https://github.com/erendikmenn/gokyuzu). Section 4(d) of the Apache License 2.0 requires anyone who redistributes Gökyüzü, or a work derived from it, to include a readable copy of the attribution notices in this NOTICE file (in a NOTICE file, in the documentation, or in a screen the software shows where such notices normally appear). The author also asks that derivative works credit Gökyüzü visibly: in the credits, "About" screen or start menu of a game, app or website built on this code, for example: Based on Gökyüzü by Mehmet Eren Dikmen — https://github.com/erendikmenn/gokyuzu (Türkçe: "Mehmet Eren Dikmen'in Gökyüzü projesine dayanır.") This visible credit is a request from the author. It does not modify the Apache License 2.0. Names and logo: the names "Gökyüzü" and "Gökyüzü SF" and the Gökyüzü logo (favicon.svg, favicon.ico, favicon-180.png, apple-touch-icon*.png) are not licensed. Apache License 2.0 section 6 grants no trademark rights. Please give a modified public version its own name and logo. You may still say that it is "based on Gökyüzü". 2. Third-party software shipped with the game --------------------------------------------- three.js 0.186 (https://threejs.org), installed from npm and bundled into the production build. MIT License. Copyright © 2010-2026 three.js authors. The build includes these three.js add-on libraries: - meshoptimizer decoder: MIT License. Copyright (C) 2016-2026, Arseny Kapoulkine. - fflate 0.8.2: MIT License. Copyright (c) Arjun Barrett. - ktx-parse and zstddec: MIT License. Copyright (c) Don McCurdy. - Draco 3D decoder (https://github.com/google/draco): Apache License 2.0. Copyright The Draco Authors (Google LLC). - Basis Universal transcoder (https://github.com/BinomialLLC/basis_universal): Apache License 2.0. Copyright Binomial LLC. B612 and B612 Mono fonts (src/avionics/fonts/). SIL Open Font License 1.1. Copyright 2012 The B612 Project Authors (https://github.com/polarsys/b612). The licence text is in src/avionics/fonts/OFL.txt. "flight" glyph from Material Icons (favicon.svg and the aircraft icons in src/ui/). Apache License 2.0. Copyright Google LLC. "settings" icon from Feather Icons (src/ui/menu.js). MIT License. Copyright (c) 2013-2017 Cole Bemis. The development tools are not part of the game and keep their own licences: esbuild, Playwright, glTF-Transform, sharp (its prebuilt libvips binaries are LGPL-3.0-or-later), draco3dgltf, meshoptimizer, KTX-Software, Blender, and the Python packages the asset pipeline uses. 3. Files in this repository under other licences ------------------------------------------------ - data/** and blender/landmarks/layout.json, blender/landmarks_ist/layout.json: Open Database License (ODbL) 1.0. See data/README.md. - tools/audio/third_party/flightgear/** and the sounds derived from them: GNU General Public License v2.0. See section 5. - src/avionics/fonts/*.ttf: SIL Open Font License 1.1. - The Gökyüzü names and logo: not licensed (section 1). - Images committed to this repository (src/ui/assets/*.jpg minimaps, docs/screenshots/*.webp screenshots): game renders under CC BY-NC 4.0, like the asset pack (ASSETS-LICENSE.md), with the data attributions of section 4. 4. Map, elevation and imagery data ---------------------------------- OpenStreetMap (both maps) Map data © OpenStreetMap contributors, available under the Open Database License (ODbL) 1.0. https://www.openstreetmap.org/copyright The committed files in data/ and blender/landmarks*/layout.json are extracts of OpenStreetMap or Derivative Databases of it, and are licensed under ODbL 1.0 (data/README.md). The OSM-derived runtime assets (city tiles, airports, landmark placement, the water, shore and land-class layers of the terrain) are Derivative Databases under ODbL 1.0 as well. The rendered world and the minimaps are Produced Works. The scripts that make these databases from OpenStreetMap are in tools/geo/ and blender/. Overture Maps Foundation (İstanbul buildings) Contains data from Overture Maps Foundation (https://overturemaps.org), release 2026-09-23.0, buildings theme, licensed under ODbL 1.0: © OpenStreetMap contributors, Overture Maps Foundation, Microsoft (ML building footprints). Copernicus DEM GLO-30 (İstanbul terrain, runway profiles, minimap relief) produced using Copernicus WorldDEM-30 © DLR e.V. 2010-2014 and © Airbus Defence and Space GmbH 2014-2018 provided under COPERNICUS by the European Union and ESA; all rights reserved The data were resampled, the airports were flattened and buildings and tree canopy were removed from the surface model. Copernicus Sentinel-2 (İstanbul imagery) Contains modified Copernicus Sentinel data 2026. Level-2A scenes of July and August 2026, accessed through Earth Search (Element 84) on the Registry of Open Data on AWS. Legal notice: https://sentinels.copernicus.eu/documents/247904/690755/Sentinel_Data_Legal_Notice EMODnet Bathymetry (İstanbul water depth) EMODnet Bathymetry Consortium (2024): EMODnet Digital Bathymetry (DTM 2024). https://doi.org/10.12770/cf51df64-56f9-4a99-b1aa-36b8d7b743a1 Licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Changes: resampled to the game's grid, filled along the shore and in narrow waters, and converted into a water-depth texture. San Francisco (US public domain and open data) - USGS 3D Elevation Program (3DEP): terrain. Public domain. Courtesy of the U.S. Geological Survey. - USDA National Agriculture Imagery Program (NAIP): aerial imagery, roof colours, minimap. Public domain. USDA Farm Production and Conservation Business Center. - NOAA NCEI DEM Global Mosaic: bay bathymetry. Public domain. NOAA National Centers for Environmental Information. - DataSF Building Footprints and Street Tree Inventory: buildings and trees. Open Data Commons Public Domain Dedication and License (PDDL). City and County of San Francisco / San Francisco Public Works, via DataSF. Airports - OurAirports (https://ourairports.com/data/): runway and airport data. Public domain. - DHMİ AIP Türkiye, AD 2: runway threshold coordinates and elevations of LTFM, LTFJ and LTBA, transcribed from the published AIP. © DHMİ. Not for navigation: the terrain, depths, runways, charts and procedures in this game must not be used for real-world navigation. 5. Sounds --------- FlightGear-derived sounds (GNU General Public License v2.0) The autopilot-disconnect sounds (the A320 autopilot button and "cavalry charge", the 737 autopilot-disconnect wailer) are derived from two FlightGear aircraft: - A320-family for FlightGear: Josh Davidson (Octal450), Jonathan Redpath (legoboyvdlp) and contributors, https://github.com/legoboyvdlp/A320-family - Boeing 737-800YV for FlightGear: YV3399 and contributors, https://github.com/YV3399/737-800YV They and the game sounds derived from them are licensed under the GNU General Public License v2.0, not under the Apache License or CC BY-NC; the asset pack keeps them in its assets-gpl/ folder with the GPL-2.0 text. The unmodified originals, the licence text and their provenance are in tools/audio/third_party/flightgear/ (LICENSE-GPL-2.0.txt, NOTICE.md) and tools/audio/third_party/CREDITS.txt. ElevenLabs Some voices and sound effects were generated with ElevenLabs (paid plan). No real person's voice was cloned. They are included in the asset pack under its licence, CC BY-NC 4.0 (ASSETS-LICENSE.md). Synthesised sounds The other sounds (engines, rotor, wind, systems, chimes, warning tones) are synthesised by the project's own scripts in tools/audio/. Reference recordings (not distributed) Some recordings were used only to measure levels and spectra; none of their audio is in the game. They are listed in tools/audio/third_party/CREDITS.txt (Wikimedia Commons, CC BY-SA 3.0 / CC BY 3.0; U.S. Navy and U.S. Air Force footage, public domain). 6. Aircraft drawings -------------------- All aircraft, airport, landmark and city models are generated by the project's own Blender Python scripts. They were drawn from public drawings and dimensions: Airbus A320 airport-planning documentation; an F-16 three-view by Marek Cel (CC0); a U.S. Air Force F-22 three-view (public domain). Photos listed in blender/**/ref/SOURCES* were used as visual reference only and are not distributed. 7. Trademarks and no endorsement -------------------------------- Airline, aircraft manufacturer, military and company names, logos, liveries and insignia shown or named in this project belong to their owners, including Airbus, A320neo, Boeing, 737, Lockheed Martin, F-16 Fighting Falcon, F-22 Raptor, General Dynamics, Sikorsky, Black Hawk, Turkish Airlines / Türk Hava Yolları, Turkish Technic, Turkish Cargo, Star Alliance, the U.S. Air Force, the U.S. Army, X, and the names of buildings, bridges and companies in the world. They are used only to identify what is depicted. Gökyüzü is an unofficial fan project: none of these organisations is affiliated with it, sponsors it or endorses it. The licences in this repository and in the asset pack grant no right to use any of these names, trademarks, logos, liveries or insignia. The asset pack contains no real airline, manufacturer or military marks; aircraft type names are used only to describe what is depicted. The live game at https://fs.erenailab.com may show brand liveries that are not part of this repository or of the asset pack. The repository and the asset pack paint fictional military markings. Where the live game shows U.S. Air Force or U.S. Army markings, they are depicted for realism only. The appearance of U.S. Department of Defense (DoD) visual information does not imply or constitute DoD endorsement. BVLOS 0.4.0 ground overlay: Geographic road/path and green-area ways in data/ist/heritage-ground.json: copyright OpenStreetMap contributors, Open Database License (ODbL) 1.0. https://www.openstreetmap.org/copyright The extract includes source element IDs, tags, bounds and timestamp and is distributed in the site/source under ODbL. Rendering colors and fallback widths are illustrative additions, not aerial photography. BVLOS 0.4.1 guide narration: music/guide-emel contains Turkish synthetic narration of the user-supplied guide using Microsoft's tr-TR-EmelNeural voice. It replaces browser-dependent speech and the removed short voice sample. No real person's voice was cloned. Text and audio fingerprints and generation settings are recorded in music/guide-emel/provenance.json. BVLOS 0.4.2 streamed aerial imagery: ArcGIS World Imagery: Esri, Vantor, Earthstar Geographics, and the GIS User Community. Tiles are delivered by ArcGIS Location Platform and are not included in this repository or asset pack. https://location.arcgis.com/help/licensing-and-attribution/