Open Source Notices
Nelkira is built on work by other people. This page lists what we redistribute, under which licence, and — where the licence requires it — how to obtain the source code. The written offer below is a legal obligation we take seriously, not a formality.
FFmpeg, and the offer of source code
Nelkira uses FFmpeg to capture the screen and encode it as video, and to decode the picture in a viewer. Which copy you have depends on the platform:
- Windows app. It ships an executable copy of FFmpeg that we build. Our Windows build is configured with
--enable-gpl --enable-libx264, which includes x264. Both are licensed under the GNU General Public License, version 2 or later, and so is this copy of FFmpeg. - macOS viewer. It ships FFmpeg 9.0.2 inside the app, as built and published for macOS by Martin Riedl. We did not build it and have not modified it, apart from replacing its code signature with an ad-hoc one so that macOS will start it from inside the app. It is built with
--enable-gpl --enable-version3and many libraries (x264, x265, libvpx, libaom, dav1d and others, listed in the build-info files in the app), so it is licensed under the GNU General Public License, version 3 or later. Its licence text and the written offer for it are in the app asFFMPEG-LICENSE-GPL-3.0.txtandFFMPEG-SOURCE-OFFER.txt. - Linux viewer. It ships no FFmpeg. It uses the distribution’s ffmpeg package, which the system installs separately under its own licence.
The copies of FFmpeg we distribute are therefore covered by the GPL. That has a consequence we are required to honour and want to state plainly:
Written offer. Nelkira Technology Ltd. will give any third party, for a period of three years from the date it received a copy of Nelkira, a complete machine-readable copy of the corresponding source code for the FFmpeg binaries we distribute and the libraries built into them, under the terms of the GPL, for a charge no more than our cost of physically performing the distribution. Write to source@nelkira.com and say which version of Nelkira you have and on which platform (for the macOS viewer, the Apple silicon or the Intel copy).
For the Windows app, that source includes the exact configuration and build script we used. For the macOS viewer, it is the FFmpeg source and the source of the libraries listed in the app’s build-info files, with the build script its builder publishes.
Nelkira itself runs FFmpeg as a separate program and communicates with it through a pipe, in the ordinary way one program invokes another. On that basis we do not treat Nelkira as a derivative work of FFmpeg, and Nelkira is licensed under our own Software Licence rather than the GPL. The GPL governs the FFmpeg binaries themselves and the libraries built into them, and the offer above applies to them.
FFmpeg is a trademark of Fabrice Bellard, originator of the FFmpeg project. We are not affiliated with, or endorsed by, the FFmpeg or x264 projects, or Martin Riedl.
Components we build with
These are compiled into Nelkira and are licensed permissively. Each remains the property of its authors, and full licence texts are installed alongside the software.
| Component | What it does here | Licence |
|---|---|---|
| .NET runtime and libraries (Microsoft) | The platform Nelkira runs on, and its encryption primitives | MIT |
| Avalonia | The windows, buttons and drawing of the interface | MIT |
| Microsoft.Extensions.Hosting | Running the agent as a background service | MIT |
| System.Security.Cryptography.ProtectedData | Encrypting stored tokens and keys (and, before release 0.4.1, the access password) to the machine or account | MIT |
| BouncyCastle.Cryptography (The Legion of the Bouncy Castle Inc.) | The password proof (SPAKE2), from release 0.4.0, in the Windows app and the Linux and macOS viewers; also inside the relay server package from relay 0.3.0 | MIT |
| MicroCom.Runtime and Tmds.DBus.Protocol | Small libraries Avalonia uses to talk to the operating system: native interfaces (MicroCom.Runtime) and, on Linux, D-Bus (Tmds.DBus.Protocol) | MIT |
| SkiaSharp and HarfBuzzSharp | Drawing the interface and shaping its text, with the native libraries they carry | MIT (the native libraries under their own licences, installed alongside) |
| ANGLE, as built by Avalonia | Drawing the interface through Direct3D on Windows | BSD-style (ANGLE licence) |
| Inno Setup | Builds the installer (not redistributed inside the product) | Inno Setup licence |
Nelkira Go
From release 0.4.0, Nelkira Go, the phone app at nelkira.com/app, includes @noble/curves and @noble/hashes by Paul Miller, under the MIT licence, for the password proof. Their notice is served beside the app as THIRD-PARTY-NOTICES.txt.
The website
This site is built with Next.js and React, both under the MIT licence, and talks to PostgreSQL through Prisma, under Apache 2.0.
Corrections
If you believe we have named a licence wrongly, missed a component we redistribute, or failed an obligation under one of these licences, please tell us at legal@nelkira.com. We would rather fix it than argue about it.