There is a jtransc script in jtransc-main-run module. You can call it directly.
Or you can use maven to execute jtransc from the command line too: mvn -f /path/to/jtransc-main-run/pom.xml exec:java
You can create a fatjar with dependencies:
mvn package at jtransc-main-run folder. It will create. target/jtransc-main-run-VERSION-jar-with-dependencies.jar and since that jar is executable you can execute jtransc with java -jar jtransc.jar.