Yeah you can embed various languages into C-based and Java-based platforms. It's not quite the same thing as the official platform being based on such languages.

The official platform will always have more mindshare, and thus support, in the way of things like:

- open source code

- developer support/discussion

- systems libraries designed with the strengths/weaknesses of the platform in mind

Play with Clojure's Java interop facilities. You'll find you get all three of those points for free.