Comment by deathanatos

IANAL.

I believe the answer would be "no". Essentially, the owners/holders of the copyright could, in theory, reach an agreement that would permit the publisher to keep publishing the game under a commercial license. That is, just because the code was licensed to you under the GPL (or available to you under that license), that doesn't mean that it had to be that way for everybody if the copyright holders struck some other deal.

Of course, here, the copyright holder is … everyone who has made changes to the kernel? Significant changes¹ to the kernel? (And see a court for the definition of "significant"?) IDK. For proprietary stuff owned by a single entity it is more straight-forward, but the very nature of FOSS makes this more interesting.

I wonder if it would only require those that worker on that file? (Can it be separated from the rest of the project? Again, IDK, ask a real lawyer!) At least that might be a shorter list of authors, and presumably you only need to involve those up to the point where the code was copied.

¹I say significant because I believe that "significant changes" is what would cause the work to become a "derivative" work, and that person to be the author of that derivative work. But in Oracle v Google, rangeCheck was sufficient for a copyright violation despite being a "trivial" function to most of us, so the bar seems pretty low?