IANAL/IANYL, but as I understand it, the Online Copyright Infringement Liability Limitation Act, passed as Title II of the DMCA, limits liability for Online Service Providers who store infringing material provided that they "comply with standard technical measures and remove repeat infringers". In addition, to benefit from these protections, OSPs must
- not receive a financial benefit directly attributable to the infringing activity,
- not be aware of the presence of infringing material or know any facts or circumstances that would make infringing material apparent, and
- upon receiving notice from copyright owners or their agents, act expeditiously to remove the purported infringing material
Again quoting Wikipedia, '"Standard technical measures" are defined as measures that copyright owners use to identify or protect copyrighted works, that have been developed pursuant to a broad consensus of copyright owners and service providers in an open, fair and voluntary multi-industry process, are available to anyone on reasonable nondiscriminatory terms, and do not impose substantial costs or burdens on service providers'.
From that, we see that it very much depends on W's terms of service, business model, and the like. If the operators of W were making money by selling access to this code, they have a problem. If they dragged their heels in taking the material down when they got the DMCA notification, they have a problem.
If W is simply running a non-commercial mirror of one or more GitHub repositories, acts expeditiously to remove the material on receipt of a notice of infringement, and doesn't have a track record of hosting infringing content, it seems to me that OCILLA will protect them as it does GitHub. But, of course, you should take proper legal advice if you start getting DMCA takedown notices.