Not a lawyer but in the scenario where proton closed the source but kept offering the build, even if gpl3 still applies since they’re the only copyright holder (no contributions) it’d only give them grounds to sue themselves?
The GNU licenses are copyright licenses; free licenses in general are based on copyright. In most countries only the copyright holders are legally empowered to act against violations.
Not a lawyer but in the scenario where proton closed the source but kept offering the build, even if gpl3 still applies since they’re the only copyright holder (no contributions) it’d only give them grounds to sue themselves?
From gnu.org:
Oh, yes but the DRM exemption clause means that you can backwards engineer the changes and continue releasing them under GPL
Edit: as an example we should probably be looking at the duckststion situation evolving right now:
https://vimuser.org/duckstation.html