Licensing

FrameTrellis is licensed under the GNU General Public License, version 3 or (at your option) any later version (SPDX: GPL-3.0-or-later). The complete license text is in LICENSE. Every source file carries an SPDX-License-Identifier header.

This document records how the license was chosen and what it means for people who build and redistribute FrameTrellis. It is a careful engineering review, not legal advice; if you plan to distribute FrameTrellis commercially or in large volumes, have the points under Open questions reviewed by a specialist.

Why GPL-3.0-or-later

The project is a community-driven editor whose maintainer wants modified, distributed versions to keep the same freedoms. A strong copyleft license does that. The choice was checked against the actual dependencies and build configurations rather than assumed:

Component	Used for	License of the parts we use	Compatible with GPL-3.0-or-later?
Qt 6 (Core, Gui, Qml, Quick, Quick Controls, Quick Dialogs, Svg, Concurrent; Test for tests)	UI, application framework	`LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only` (verified in the Qt 6.8.3 sources) — we use it under LGPL-3.0 / GPL-3.0	Yes
Qt Shader Tools	Build-time tool for Qt Quick only; not linked	GPL-3.0 with Qt exception / LGPL-3.0	Not distributed with the app
MLT framework, `core`, `avformat`, `plus` modules	Timeline graph, playback, encoding	`LGPL-2.1-or-later`	Yes
MLT `normalize` module (the `volume` filter)	Clip volume and audio fades	`GPL-2.0-or-later`	Yes ("or later" allows GPL-3.0)
FFmpeg (through MLT)	Decoding and encoding	`LGPL-2.1-or-later` by default; `GPL-2.0-or-later` with `--enable-gpl`; `GPL-3.0-or-later` with `--enable-gpl --enable-version3`	Yes, for every configuration except `--enable-nonfree` builds, which may not be redistributed at all
x264 (inside GPL FFmpeg builds)	H.264 encoding	`GPL-2.0-or-later`	Yes
SDL 2	Audio output (optional)	`Zlib`	Yes
FrameTrellis artwork and icons	Logo, icons	Original work, `GPL-3.0-or-later`	—

Because the H.264 encoder that makes the documented MP4 export possible (x264) is only available in GPL builds of FFmpeg, and because MLT's volume filter is GPL-licensed, a binary FrameTrellis distribution is a GPL work in practice. Choosing a permissive license for FrameTrellis would not change that for binaries and would weaken the protection the maintainer asked for. Nothing in the stack is GPL-2.0-only, which would be the one incompatibility to watch for: Qt is also offered under GPL-2.0-only, but we use its LGPL-3.0/GPL-3.0 options.

The project license versus dependency licenses

The FrameTrellis source code, documentation, website and artwork in this repository are GPL-3.0-or-later unless a file says otherwise.
Dependencies keep their own licenses. They are listed in THIRD_PARTY_NOTICES.md. Using them under GPL-3.0-or-later does not relicense them.
Media you edit and the files you export belong to you. The license of the software does not apply to your footage or output.

Building from source

When you build FrameTrellis yourself, you link against whatever Qt, MLT and FFmpeg your system provides. All common distribution packages (Ubuntu/Debian, Fedora, Arch, MSYS2, Homebrew) are GPL-compatible. Do not link FrameTrellis against an FFmpeg built with --enable-nonfree if you intend to redistribute the result: such builds are not redistributable.

You can check an FFmpeg build with ffmpeg -buildconf (look for --enable-nonfree).

Redistributing binaries

If you distribute FrameTrellis binaries (including the project's own release packages), the GPL and LGPL require you to:

Ship the license texts. Packages include LICENSE, THIRD_PARTY_NOTICES.md and, for the Windows package, the license files of every bundled library. Where an MSYS2 package installs no license file, the packaging script takes the texts from its upstream source, and the package build fails if any bundled component would be left without one.
Provide the Corresponding Source for FrameTrellis and for every bundled GPL/LGPL library (Qt, MLT, FFmpeg and FFmpeg's GPL dependencies such as x264), for the exact versions shipped. For FrameTrellis this is the tagged source in this repository. Each Windows package contains BUNDLED_COMPONENTS.txt (every bundled MSYS2 package with its version and license) and SOURCES.txt (the matching MSYS2 source packages). The release workflow downloads those source packages (build recipe, patches and upstream source) and attaches them to the release as FrameTrellis-<version>-windows-x64-third-party-sources.tar, so the project itself keeps the Corresponding Source available next to the binaries.
Allow relinking of LGPL libraries. Qt and the LGPL parts of MLT/FFmpeg are shipped as separate shared libraries (DLLs), so users can replace them. Static linking is not used.
Not add restrictions. No DRM, no additional terms, no "non-commercial" conditions.

Windows packages

The Windows package is built with the MSYS2 UCRT64 toolchain and bundles MSYS2's Qt 6, MLT and FFmpeg DLLs. As verified in the MSYS2 package recipes used at the time of writing:

FFmpeg is configured with --enable-gpl --enable-version3 and without --enable-nonfree, so its effective license is GPL-3.0-or-later and it is redistributable.
MLT is built with its default GPL=ON/GPL3=ON options, so its GPL modules are present.
SDL 2 is Zlib.

The bundled set is determined at packaging time, so the manifest generated for each release is the authoritative list for that release.

Container image

The frametrellis-render container image in GitHub Packages contains FrameTrellis's renderer and Debian 13 packages of Qt, MLT, FFmpeg and their dependencies. The image keeps Debian's license files (/usr/share/doc/<package>/copyright) and lists every Debian package with its exact version in /usr/share/doc/frametrellis/debian-packages.txt; the corresponding source of each of them is available from the Debian archive and from snapshot.debian.org at that version. The FrameTrellis license and third-party notices are in /usr/share/doc/frametrellis.

Patent-encumbered codecs

Some formats (notably H.264/AVC, H.265/HEVC and AAC) may be covered by patents in some countries. Copyright licenses such as the GPL do not grant patent licenses from third parties. FrameTrellis does not charge for the software and does not include any patent license. If you distribute FrameTrellis commercially, check the rules that apply in your country.

Open questions

These points have been considered but would benefit from specialist review before large-scale commercial redistribution:

Whether the MSYS2 source packages attached to each release are complete for every component. They are what MSYS2 publishes as the source of its binaries, but a component whose recipe fetches additional sources at build time could need extra archives.
Patent licensing for H.264/AAC in jurisdictions where those patents are still enforceable.

Contributions

By submitting a contribution you agree that it is licensed under GPL-3.0-or-later, the same as the project (inbound = outbound). There is no contributor license agreement and no copyright assignment; contributors keep their copyright. Please add an SPDX header to new files.

This page is generated from docs/LICENSING.md in the repository. Found a mistake? Open an issue.