questions about capabilities of mozilla-java interoperation

Hi, friends

There days I'm thinking about choosing a new platform for our product,
between Mozilla/XUL and Eclipse. The most important thing taken into account
is the extensibilities (both the lower level and the UI level).  Some of our
clients want our product can give some chances for them to extend the
functions and integrate their tools in. As the product is for end users, I
don't like the memory overhead of Eclipse.

Now I'm trying to find out what role Java could play in Mozilla/XUL
platform, but get lost in a forest of jargons: LiveConnect, BlackConnect,
Blackwood, OJI, JavaXPCOM, Webclient...    Could somebody shed some light on
what these are meant for? Which ones are meant for using Java inside
Mozilla, and which ones for connecting and commanding Mozilla from outside?
It seems that some projects are now out-dated or deprecated, but LiveConnect
and JavaXPCOM are being actively developed. Is that true?

And I also noticed that the incoming Eclipse 3.3 can embed XULRunner as its
web browser. But can I command it to navigate to chrome:// urls? Can I
manipulate the element DOM tree in Java? Can I add event listeners? From the
docs I found. It seems yes. But I don't know whether there're some limits or
drawbacks.

Sorry for so many questions :-)
best regards
Ralph Young