Even if you finish your rewrite and then release it, the final product might still be a derivative work of the original, because "translations" are legally codi

Even if you finish your rewrite and then release it, the final product might still be a derivative work of the original, because "translations" are legally codified as derivative works. Of course, this is bounded by the merger doctrine and various court cases regarding software compatibility. If you can show that everything in your version has to be structured the same way as the original in order for it to read and write ZFS volumes, thus making it a sort of 'external interface', then you probably have good ground to stand on against Oracle. But things like source file structure or internal call chains are unlikely to constitute an interface in a filesystem driver. The closest legal example of a "file-by-file rewrite" would be BSD; but the lawsuit they got from UNIX System Laboratories was settled, so it creates no precedent. The reason why the reverse engineering crowd talks a lot about clean-room is because you naturally discover the interface boundaries as part of the development process. Legally speaking, you don't need two separate and isolated groups of people, but starting from a document of how the system 'should' work and then adding in implementation details that you actually need is a good way to avoid accidentally copying things you don't need to.