Open-source at least non-core technologies like JMF
The "compatibility" issue really only applies to things that are distributed with J2SE, J2ME, or J2EE. If it is a separate download, a separate install, then in general, it is going to be the developer who has to get their users to install it; the user won't already have it.
Take JMF (Java Media Framework) for example: what user would already have this installed? None, unless you have Java Desktop.
JMF is also among a number of technologies that are being arguably neglected by Sun. Great ideas, incomplete implementation. A number of important protocols missing (MPEG4), weak support for some platforms. If Sun is going to focus its priorities elsewhere, how about open-sourcing things like JMF, and let others who need it turn it into what it should be.
I'd like to see a review of all the non-core technologies that are not a "compatibility" issue, and open-source (as in LGPL) those that are appropriate.