The free community version of Rustdesk Server (a competitor to the Teamviewer remote access software) is AGPL licensed.
https://github.com/rustdesk/rustdesk-server
The paid, proprietary Pro version builds on top of the community edition by adding extra features such as user authentication and a web backend for administration.
There exists a repo for the pro server: https://github.com/rustdesk/rustdesk-server-pro
But it only contains install scripts and no actual source code of the application.
The github releases page of this repo however, contains the compiled code of the proprietary pro version and is available for anyone to download for free.
Analyzing the disassembly of the pro and open source binaries shows that the pro version is definitely based on the open source version.
The company previously associated with Rustdesk, Purslane Limited of the UK, is no longer in operation since 2023.
The project has no CLA and so the dozens of previous contributors still hold the copyright to their code and have not given permission for it to be used in a proprietary version.
There have been multiple requests for the source code of this pro version, but either there was no response or the issue was closed without comment.
EDIT: The repo owner has completely deleted the issue, here is a screenshot: https://0x0.st/KaqD.png
To me this just proves they know what they’re doing is wrong.
The copyright holder doesn’t legally have to follow the terms of their own license. It sucks that it’s not FOSS, but this isn’t a violation unless there are contributers who didn’t consent to a proprietary distribution.
That would include changes made later on in the OSS version, that were backported to Pro without permission from the original authors.
Did they accept PRs from people? If so, then yeah, that’s illegal.