Quoting russell@coker.com.au (russell@coker.com.au):
Oracle has not chosen to persue any action against Canonical.
More to the point, so far, so have the Linux kernel coders. But the copyright violation is real, and Canonical risk either set of stakeholders filing and getting them severely sanctioned and that practice terminated at any time.
In any case it's not a problem for people who use Ubuntu.
I personally don't like dealing with companies that indulge shady business practices that violate the ethics of the open source community, and this isn't the first time Canonical have done so. Moreover, I personally eschew dealings with firms inclined to make potentially fatal legal mistakes. As to customer legal liability, probably as you say, but I wouldn't rule that out. https://www.law.cornell.edu/wex/contributory_infringement