First off, IBM and HP maintain their own JVMs (as did Microsoft until the Sun/MS lawsuit). Secondly, Apple insisted on being the one to port their JVM. Reading the blog post by Gosling will tell you that. And thirdly, they didn't do it "for free" (at least in the early days - not sure about the last few years). I was at Javasoft back then, and Sun funded some Apple engineers to work on the port.
I don't have a problem with someone else (say, Sun^H^H^HOracle) doing the port - it would be more timely, up-to-date, etc. I just wish they would have had a something worked out saying "We're not gonna support our JVM, and Oracle will be doing this starting on
in the Boston Globe: http://www.boston.com/news/local/articles/2007/03