Sky Map v2
Copyright © 2026 Penterakt LLC and the Sky Map contributors.
This module is licensed under the GNU General Public License v3 or later (see
LICENSE.md). It carries a single file inherited from Sky Map v1 under the
Apache License, Version 2.0, recorded here.
One file: the compass-calibration animation,
app/src/main/assets/calibration/calib.gif. It was added to Sky Map v1 in 2016 — after the
January 2012 Google open-source release — so it is not Google-authored. It is inherited under
v1’s Apache-2.0 licence, and its authorship has not been established.
No Google-authored material remains in v2. The two time-travel sound effects, which shipped as
.wav in the 2012 release and were later transcoded, were the last of it; they were removed
entirely rather than carried forward.
Sky Map v1 ships no NOTICE file, so Apache-2.0 §4(d) is not engaged; this file exists to satisfy
§4(c) for the item above. Should calib.gif prove to be the project’s own work, or be replaced,
this file can be deleted — nothing else in v2 requires it.
This section exists because an earlier draft of this file overstated the position, and an overstated notice is not a neutral error: it would imply that substantial parts of v2 are available under permissive terms when they are not.
The source code is an independent reimplementation, not a port. v2 was written to match v1’s
behaviour, which is not protectable subject matter. Where the two are compared directly the
implementations diverge: RaDec moved from mutable Float to immutable Double with a different
API and corrects a v1 sign-handling bug in decDegreesFromDms; TextureCache caches eclipse and
phase geometry and bears no relation to v1’s resource-ID-keyed TextureManager;
LabelAtlasPacker is an original design. No Google-authored source is redistributed.
The translations are not Google’s. 29 locale resource sets were carried across from v1. Of the
strings that survive from the 2012 Google release, the remainder are isolated single words —
Sonne, Mond, NORDEN, ZENIT — which are dictionary terms rather than copyrightable
expression, and for which only one correct translation exists. Everything else post-dates 2012 and
is the work of Sky Map’s community translators, credited in
app/src/main/res/values/contributors.xml. v1’s string resources carry no copyright notice, so
§4(c) has none to retain.
Star catalogs, ephemeris data and celestial imagery are governed by their own terms, which are not
uniform: some are public domain (NASA, ESA, JPL, USNO), others are CC BY 4.0 (ESO, the IAU,
IAU/Sky & Telescope, the EHT Collaboration). CC BY 4.0 is not public domain and carries ongoing
attribution obligations. Full attribution is in the app’s credits screen,
app/src/main/res/values/credits.xml, and in app/src/main/assets/planets/SOURCES.md.
Classification of every shipped asset is in ASSET-LICENSES.txt.
Contributions are made under the Sky Map Individual Contributor License Agreement (CLA.md at the
repository root). Contributors retain copyright in their work.