Open source

Last updated: 2 October 2026

Kepler is built with open-source software. Each app lists every component it includes, with its licence and the licence's full text: on Android, under Settings, Open-source licences, and on iPhone, iPad and Mac, under More, About, Open-Source Licenses. This page is where the source those licences ask us to offer can be found.

FFmpeg in Kepler for Android

Kepler for Android decodes some audio formats (AC-3, E-AC-3, DTS, TrueHD, MPEG audio and others) with FFmpeg, through the FFmpeg decoder extension of Google's Media3 library, and, from version code 11, MPEG-4 Part 2 video (Xvid, DivX) on devices without a decoder of their own for it. FFmpeg is licensed under the GNU Lesser General Public License, version 2.1 or later. It was configured without its GPL and non-free options, and FFmpeg itself is used unmodified.

FFmpeg

6.0.2, release/6.0 branch at commit b4a62c32549b8295691a8e0ff2c9b82188923159

Media3 extension

1.10.1, libraries/decoder_ffmpeg (Apache License 2.0)

Kepler's addition

From edition 2, one source file for the video decoder (Apache License 2.0), compiled into the same library

Built with

Android NDK r26b, API level 24; armeabi-v7a, arm64-v8a, x86 and x86_64

In the app

Linked into libffmpegJNI.so, a separate shared library the app loads at run time

Download the source

Edition 2 (Kepler for Android 1.0, version code 11 and later; audio decoders, and the MPEG-4 Part 2 video decoder): kepler-ffmpeg-6.0.2-b4a62c3-media3-1.10.1-edition2.tar.xz 9.9 MB, tar.xz

SHA-256 8e813441917722c9ef73fb9b0da207f934959f56576dc73d319062c02a71d9ab · README

Edition 1 (Kepler for Android 1.0, version codes 4 to 10; audio decoders only): kepler-ffmpeg-6.0.2-b4a62c3-media3-1.10.1.tar.xz 9.9 MB, tar.xz

SHA-256 defe733274d643fbfa3c69792dc470358f47d6d4239576663b95c11b0489cd71 · README

Each archive holds FFmpeg's source at that commit, Media3's FFmpeg extension (the JNI glue and the script that runs FFmpeg's configure), Kepler's own added source where there is one, and the script Kepler's build uses to put them together, with a README naming every option. It is everything needed to rebuild that edition's libffmpegJNI.so.

FFmpeg in Kepler for iPhone, iPad and Mac

Kepler for iPhone, iPad and Mac repackages Matroska films for Apple's player with FFmpeg, and converts the sound formats Apple's player cannot play (DTS, TrueHD, MP2, MP3) to E-AC-3. FFmpeg is licensed under the GNU Lesser General Public License, version 2.1 or later. It was configured without its GPL and non-free options, and the release is used unmodified.

FFmpeg

9.0.2, the release as published

Built with

Xcode 26.2; iOS 17, macOS 14 and tvOS 17 or later

In the app

Linked into FFmpeg.framework, a separate dynamic framework the app loads at run time

Edition 1 (Kepler for iPhone, iPad and Mac 1.0 and later): kepler-apple-ffmpeg-9.0.2-edition1.tar 12 MB, tar

SHA-256 82bf0d02bc31563d22c7c2bd5844fbd0cc7e56994db0ab483f0a3ecb47acdbc6 · README

The archive holds the FFmpeg release as published, the script Kepler's build uses to build it, and a README naming every option. It is everything needed to rebuild the app's FFmpeg.framework.

VLCKit in Kepler for iPhone, iPad and Mac

Kepler for iPhone, iPad and Mac plays the films and streams Apple's player cannot open with VLCKit, VideoLAN's framework around libVLC. VLCKit and libVLC are licensed under the GNU Lesser General Public License, version 2.1 or later; the libraries it is built with carry their own licences, listed in the app. Kepler ships VideoLAN's own build of VLCKit, unmodified. Its source is made of these parts:

VLCKit

4.0.0a25, commit 8f5ce02f09a7da5d061a24ddac3cb432f2a9b332

VLC (libVLC)

Commit 005e69e67a8730f128e44bde68437fbb048cf45f, with the 12 patches in VLCKit's libvlc/patches applied

Libraries

The source releases VLC's contrib system fetches for iOS and macOS with VLCKit's options, each checked against the checksum in its rules

In the app

Linked into VLCKit.framework, a separate dynamic framework the app loads at run time

All of it together, with the steps to rebuild the framework, comes to about 550 MB, and we send it as one archive on request.

Source on request

For at least three years after we last distribute a build containing them, we will also send the complete source of each component on this page on request (for VLCKit, the archive described above), on a physical medium if you need one, for no more than the cost of providing it. Write to contact@keplerplayer.com.

Everything else

The other components are under permissive licences (Apache 2.0, MIT, BSD), and the apps' typefaces (Sora, Instrument Sans and JetBrains Mono) under the SIL Open Font License 1.1. None of these asks for source to be offered; their notices and full texts are in each app's list, which on iPhone, iPad and Mac also names every library built into VLCKit.

Contact

Questions about open source in Kepler: contact@keplerplayer.com.