What is their official position towards clojure?
Sun is not a single mind. You will find opinions on clojure that are all over the map:
http://www.google.com/search?source=ig&hl=en&rlz=&q=site%3Ablogs.sun.com+clojure&aq=f&oq=&aqi=
And don't forget, a lot of non-Java languages running atop the JVM can take advantage of those vast libraries, both within the JDK and without. I think Sun generally approves of such reuse.
The most optimistic success case for Clojure is probably defined relative to the other Lisp variants. Should Clojure lead the Lisp army (unlikely, BTW, but that's another question) it still would not have much economic effect.
And if it doesn't have much economic effect, then it won't really have a conventional wisdom inside a corporation. Individuals there will like it and dislike it, but as a company, they just won't care one way or another.
Should hell freeze over and then everone starts developing in Clojure, the company probably still wouldn't care, they would just find a way to adapt and live in the new ecosystem. As time went on a story would develop about how it was all their idea to start with.
I don't know of any "official" position of Clojure. You may have seen reports of work on supporting dynamic languages on the JVM and hosting JVM language summits at the Santa Clara campus. The general attitude seems to be, if you want to do some programming, please come and do it on the JVM.
Why should Sun/Oracle (as a whole), empoyees, or any of the millions of users of said Java libraries or JVM care about Clojure except how Clojure is beneficial (or detrimental) to individual tasks?
The question is, well, silly at best.
Clojure will not replace Java -- it was not even designed to -- and, if anything, simply showcases the adaptability of the JVM (and the layers of hacks used to support dynamic languages in relatively efficient ways). Hopefully the JVM will flourish and improve (and will have better support for "non-Java" programming models).
There is no reason at all why sun might be "not too excited" about alternative JVM languages (and there are lots of languages besides Clojure: Groovy, Scala, JRuby, Jython, even JavaFX which is from Sun itself).
I think all those new languages are important for the JVM, and Sun is actively working on adding support in the JVM for alternative programming languages (see JSR 292, for example).
It's not like as if Sun wants everybody to use the Java programming language only...