The src sub-directory contains modules included in Apache SIS releases, but which are buildable or executable only if some dependencies are added by the users themselves. Those dependencies are not distributed with Apache SIS releases because they are under more restrictive licenses than Apache 2. If those dependencies are not provided, Apache SIS endorsed modules will still work but without Graphical User Interface (GUI).
Paths to dependencies are specified by the following environment variables. After those variables are set, gradle assemble can be executed as usual.
JavaFX is licensed under GPL with classpath exception. The JavaFX SDK can be downloaded from the OpenJFX web site and installed in any directory. The path to the directory containing the JAR files is specified in Unix shell as below (change the /usr/lib/jvm/openjfx path as needed):
export PATH_TO_FX=/usr/lib/jvm/openjfx
A ZIP file containing a subset of Apache SIS modules and dependencies is built in the build/bundle/ sub-directory. That ZIP file can be unzipped in any directory. The application is launched by running the ./bin/sisfx script.