This project is structured using the Standard Directory Layout for Maven projects, with two child modules, core, alias-test, system-test, and installer. In addition, there is a documentation directory containing project documentation.
The core module contains the main source code for the project. core includes Jython modules and Java classes, as well as typedef files, alias definitions, and the message bundle.
The system-test and alias-test modules contain test suites for verifying pull requests and nightly regression testing.
Alias definitions are discussed in more detail here.
The installer module builds the final installer ZIP file. installer includes the assembly definitions, start scripts for each tool for Linux and Windows platforms, and configurations for variable injection and logging.
Two installer files are built under the WLSDEPLOY_HOME/installer/target directory, one ZIP file for all platforms, and one tar.gz file for those that prefer the tar.gz format on UNIX systems.
There are detailed instructions for building the project here.