Ant was initially designed to be a build maintenance utility - but now it has a whole lot of projects that extend its features beyond its original intentions. To know more about the same - visit Ant Apache home page.
Doxygen is a document generation utility that is used to generate a variety of documents (html/pdf/hlp/dot - among others) from the given set of source files, by parsing the structures and comments in the same.To know more about the same - visit Doxygen home page.
This project released under Apache License, contains the jar task that helps an Ant build maintainer to integrate doxygen tasks with the same. The ideal target audience of the same would be build maintainers and release engineers of the projects who can integrate this Ant Task with the rest of the release system to generate a set of documentation from the latest version of the source tree.
Update:
Dec 30 2008: Ant 1.6.1 released. See the Download page for options.