I read some messages at
http://groups.google.com/groups?hl=en&safe=off&group=netscape.public.mozilla.license
Conclusion is
1) I can distribute software based on mozilla. And I don't have to
provide source code "fully" written by me.
2) I need to provide code which modifies behaviour of mozilla. So if
I modify some mozilla component say 'html parser' then I need to give
it's source code.
3) If mozilla is not fully functional without my program then I have
to provide source code for my program too.
Is this the essence of 'the MPL/NPL or whatever license we follow at
mozilla' for a software developer.