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No, the Python on Java is called Jython. And it has much more use than Groovy, since it's not limited to JVM. You can do amazing things with Python, with things like Twisted, PyPy, Freshen, etc.

I use Python and as you said is great but really Jacek Jython lacks behind and is slow compared to Groovy. Also Groovy blends very well with the JVM and the 2.0 with static compilation will rock the house.

He says that JRuby, Jython etc. failed, but i do not think so. Both are active projects and for example JRuby gives opportunity to install RoR apps in many big companies that support only Java in production. These projects are sometimes very useful in practice, not failed at all.

Good to see an article about Groovy. In my opinion, a much better choice as an Java alternative then Scala or Clojure. Groovy is very much mature and a solid alternative, if you want dynamic/static typing, functional programming, and more syntax sugar.

I'm using it exclusive for my JUnit tests, because it's much more readable to use Groovy then Java. Also for my GUI applications, because Groovy code is again more readable and shorter.