This project is split-licensed, because the historical border data it builds on carries a copyleft licence that the code does not need to inherit. See ATTRIBUTION.md for the sources and their credits. In short, and in order of precedence (a file or text named in a later section is NOT covered by the MIT section, whatever directory it sits in): 1. Code ............................................ MIT 2. Historical border data (everything prep-hist.mjs writes) ... CC BY-SA 4.0 (adapted from historical-basemaps, CC BY-SA 4.0, and Atlas Fontium, CC BY 4.0) 3. Physical geography and modern borders .......... public domain 4. Portraits (public/portraits/) ................... each under its own licence 5. Written prose (data files and interface) ........ CC BY-SA 4.0 ================================================================================ 1. CODE — MIT License ================================================================================ Applies to: everything under src/ and scripts/, and the build and deployment configuration, EXCEPT: - the border data in section 2 (src/data/geo/historical.json, src/data/geo/precision.json and every file under src/data/geo/backdrop/); - the geography data in section 3 (src/data/geo/land.json, modern.json, hydro.json); - the portrait images in section 4 (public/portraits/); - the written prose in section 5 (the natural-language text inside src/data/periods.ts, leaders.ts, people.ts, events.ts, longEvents.ts and cities.ts, and inside src/i18n.ts). The code, types and data structure of those .ts files are MIT; only the prose strings inside them fall under section 5. Copyright (c) 2026 the polska-timeline authors Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. ================================================================================ 2. HISTORICAL BORDER DATA — CC BY-SA 4.0 ================================================================================ Applies to: every file scripts/prep-hist.mjs writes, which today is - src/data/geo/historical.json - src/data/geo/precision.json - every file under src/data/geo/backdrop/ — one per snapshot year, both the years lifted straight from the source and the years derived from it — including any file added to that directory in future; - public/share.png, the link-preview picture scripts/make-share-image.mjs draws from these outlines. Derived from historical-basemaps by André Ourednik (https://github.com/aourednik/historical-basemaps), licensed CC BY-SA 4.0. Also adapted from the GIS layers of Atlas Fontium, published by the Tadeusz Manteuffel Institute of History of the Polish Academy of Sciences (IH PAN) at https://data.atlasfontium.pl/, each licensed Creative Commons Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/). CC BY 4.0 material may be included in a CC BY-SA 4.0 adaptation; the credit it requires is given here, in ATTRIBUTION.md (which lists every layer used) and in the in-app Sources panel. The layers were clipped, simplified and combined with the historical-basemaps and Natural Earth geometry by set operations. Modifications: clipped to Central Europe, simplified (Douglas-Peucker), renamed and merged by polity, and in places combined by set operations to derive shapes and whole snapshot years not present in the source — for example the partition zones, computed by intersecting the Commonwealth with the partitioning empires' own later borders, and the years between the source's snapshots, derived from the nearest one. Some later backdrop years are built wholly or partly from Natural Earth (section 3); that public-domain geometry stays public domain, and the CC BY-SA licence on those files adds no restriction to it. See scripts/prep-hist.mjs. As an adaptation of CC BY-SA material, these files are themselves licensed under Creative Commons Attribution-ShareAlike 4.0 International: https://creativecommons.org/licenses/by-sa/4.0/ These files may NOT be relicensed under the MIT terms above. ================================================================================ 3. PHYSICAL GEOGRAPHY AND MODERN BORDERS — Public domain ================================================================================ Applies to: src/data/geo/land.json, modern.json, hydro.json Derived from Natural Earth (https://www.naturalearthdata.com/), which is in the public domain and requires no permission or attribution. Credited anyway. ================================================================================ 4. PORTRAITS — individually licensed ================================================================================ Applies to: every file under public/portraits/. These are 120px thumbnails copied from Wikimedia Commons, unchanged but for their size, and served with the site. They are NOT covered by the MIT or the CC BY-SA terms above: each stays under its own licence, which is recorded with its author and its Commons file page in src/data/portraits.json and shown in the application's Sources panel for every portrait on screen. Each is public domain or licensed CC0, CC BY or CC BY-SA. ================================================================================ 5. WRITTEN CONTENT — CC BY-SA 4.0 ================================================================================ Applies to: the descriptive prose — summaries, narratives, role lines, event titles and descriptions, anniversary lines, notes — inside src/data/periods.ts, leaders.ts, people.ts, events.ts, longEvents.ts and cities.ts, and the prose of the interface in src/i18n.ts (the map notes, the About panel's texts, the privacy notice). Not to the code, types or structure of those files (MIT, section 1), and not to the facts they record — names, dates, figures, coordinates — which are not copyrightable by anyone. Original work written for this project. Released under CC BY-SA 4.0 for consistency with the border data it accompanies. No text is taken from Wikipedia or any other encyclopaedia.