I thought Sun released most of Java code under open-source licenses years ago[1]. Are there key parts of Java which are closed-source and only those parts are d

I thought Sun released most of Java code under open-source licenses years ago[1]. Are there key parts of Java which are closed-source and only those parts are disputed? If that's the case it shouldn't be very hard to replace those parts. I'm not familiar with the Java ecosystem. I appreciate if you could correct me. [1] http://www.gnu.org/philosophy/java-trap.html http://www.gnu.org/philosophy/java-trap.html