Sun is a company, and companies are in this for the money, not because they love open source. What else are you expecting Sun to do for open source (because they really did a lot already), and what would they have to gain out of it? Don't you think that maybe, just maybe, Sun needs some proof that open sourcing actually benefits them, before doing something we all want, like open sourcing Java? What better proof could they expect other than having people help them by contributing to the development of projects like OpenOffice?

Now, returning to your Linux question, why would Sun want Linux to succeed, when they already have a viable recently open sourced operating system like OpenSolaris? The answer is pretty simple, I think: because Microsoft's world domination hurts them tremendously. Maybe they cannot fight Microsoft in the open any more without the risk of getting totally crushed, because now they are small, compared to what they were several years ago at least. But they will surely try to support any alternative to Microsoft's products, Linux included. That is why they bought StarOffice in the first place, isn't it?