What is that

The tools are designed as library projects. I prefer to keep a whole copy of the project in my workspace, include it in my own project and simply exclude classes which I don't use from build path. This is also the safest approach for incoming updates and improvements. But you can also strip the needed tools from the project and put it in your project directly.

While excluding and stripping unused classes you have to take care of the dependencies. Those are always documented at the bottom of each class documentation.