I expect that for games the more important piece will be the art assets - like how the Quake game engine was open source but you still needed to buy a copy of the game in order to use the textures.
They had gotten surprisingly close to a complete decompilation, but then they tried to request a copy of the source code from the copyright office citing that they needed it as a result of ongoing unrelated litigation with Nintendo.
Later on this killed them in court.
That's very different from the decompilation projects being discussed here, which do distribute the decompiled code.
These decompilation projects do involve some creative choices, which means that the decompilation would likely be considered a derivative work, containing copyrightable elements from both the authors of the original binary and the authors of the decompilation project. This is similar to a human translation of a literary work. A derivative work does have its own copyright, but distributing a derivative work requires permission from the copyright holders of both the original and the derivative. So a decompilation project technically can set their own license, and thereby add additional restrictions, but they can't overwrite the original license. If there is no original license, the default is that you can't distribute at all.