The build and execution requires at least Java 11. To build execute
mvn clean install
on a shell. Usually the build result can be found in the target folder:
KiCad2HAL-1.0.0-jar-with-dependencies.jar
In eeschema open File->Export->Netlist and add a new generator (button "Add Generator..."). Select a title and add
java -jar <path to jar>/KiCad2HAL-1.0.0-jar-with-dependencies.jar "%I" "%O.hal"
Change the to the folder where you placed the jar.
To convert a LinuxCNC schema to HAL click Button "Export Netlist".