They didn't change the license of old JDKs AFAIK (correct me if I'm wrong). So, those big companies would first have to switch to an affected version of the JD

They didn't change the license of old JDKs AFAIK (correct me if I'm wrong). So, those big companies would first have to switch to an affected version of the JDK anyway, so they could as well switch to OpenJDK.