how does a clean-room implementation of anything works anyway? people personally testify that they haven't seen the thing they want to cleanroom implement, right? and what if they did see it, how would anyone know/catch them? something is too similar is not proof. what if the implementer read a random comment on it on HN that laid out the general architecture of the thing, does make the result a derivative work?
I think the fear of copyright infringement from developers being "tainted" by seeing or hearig about some software/implementation is exaggerated.
Copyright only applies to expression (code) not ideas. It would be extremely hard for anyone to re-implement anything in a matter exact enough to be plagiarism.
For a clean room impl the fear would be patents, not copyright.
Any software lacking patents can (my armchair lawyer guess) safely be re-implemented. If people reimplementing have had past access to the source code of the original, that's probably not even a great danger, so long as nothing is copied verbatim. Ideas/designs/architecture/functionality is not protected by copyright.
