i don't think that's consistent with history. there used to be a large number of Java implementations; by far the biggest reason why they (almost) all died out

i don't think that's consistent with history. there used to be a large number of Java implementations; by far the biggest reason why they (almost) all died out is because Sun agreed to open up their implementation. IBM still maintains J9, and while that's only part of a full Java implementation, I don't see any reason why Apache Harmony or GNU Classpath couldn't be revived and combined with it for a high-performance Oracle-less Java implementation. there is major precedent for this in the form of GNU/Linux, where substantial parts of the userspace are provided by GNU, but the kernel is a separate project.