This is GooTool, an addin manager and customisation tool for World of Goo.
More details on its features can be found at http://goofans.com/gootool
You can find addins to use with GooTool at http://goofans.com/world-of-goo/expanding-world-of-goo/downloads
Issues and pull requests are welcome in this repository. General discussion should be on the forum at http://goofans.com/forum
This software may be used under the terms of the GooTool license: https://github.com/davidc/gootool/blob/master/dist_src/common/doc/LICENSE.txt
This is currently a copy of the SVN repository as of September 2012. The branch 1.0.4-dev is only minor updates from the last released version. The trunk contains a lot of unreleased development work that separates out "target" worlds that are built (this was done to allow for remote targets over SFTP, e.g. on iOS). I believe this is working but it involved a rewrite of a large chunk of the core code and it has not had substantial testing as yet.
The tool builds with ant with only two external dependencies (three if you build the NSIS installer). These are listed and their locations are set in ant.properties.