Open source licenses for decompilations, are they valid or not?

[Trilarion]

There are some projects like https://github.com/rep-stosw/tube64.git or https://github.com/LostArtefacts/TR1X.git or #399 that claim to be GPL or MIT licenses but are based on decompilations of proprietary binary code. Unless these projects have the explicit permission of the original owner of the code, this should be illegal and they should excluded from this list here, which focuses on legal open source licenses.

On the other hand there is often a lot of work and no commercial interest in these project, so it would be really nice if it was actually possible to use a the claimed licenses. Maybe ask (https://law.stackexchange.com/ or https://opensource.stackexchange.com/) for a legal estimation or suggest to ask the original owners if they can allow this usage for the respective projects.

On the other hand asking the original owners might awake sleeping dragons and make things worse.

On the other hand, decompilation is nothing like a clean-room (only your own sweat) effort. I doubt there is any way it can be legal withing the next 70 years (or as long as copyright duration is).