The latest launcher version can be downloaded from the releases page.
To compile the launcher you need to use Maven. Most IDEs have maven integration out of the box.
To compile simply run maven with the package goal. After compiling a folder called target will be created containing a jar called alterorb-launcher.jar, use this jar to start the launcher.
The jars that AlterOrb uses are pre-patched, to reproduce the jar builds or simply see what/how is being patched out checkout the AlterOrb's patcher project.