Assuming both checkboxes are selected, the user now has (assuming OK is clicked) two new Ant scripts in the nbproject folder:
Let's look at each of them. Here's exactly what you get:
And now you need to add those JARs (in the case of the Groovydoc script, you need a snapshot build, since it isn't supported yet officially) and then simply use those Ant scripts. It would be really cool if they would be linked into the main build.xml, automatically, in the same way as the build-impl.xml is. However, I am not sure if that is possible to do automatically. Although, actually, I think I've done something similar before. I need to investigate that.
At any rate, I will add the sources of the module that provides this functionality to http://nbgroovysupport.dev.java.net/.