On v1.1.2, the tools cannot convert to a Turtle formatted file.

$ java -jar ./tools-java-1.1.2/tools-java-1.1.2-jar-with-dependencies.jar Convert ./spdx-spec/examples/SPDXRdfExample-v2.3.spdx.rdf.xml /tmp/foo.rdf.ttl
WARNING: sun.reflect.Reflection.getCallerClass is not supported. This will impact performance.
16:24:26.801 [main] ERROR org.apache.jena.util.JenaXMLInput - Problem setting StAX property - name: "http://javax.xml.xmlconstants/property/accessExternalDTD" - value: "" - error: Unrecognized property 'http://javax.xml.XMLConstants/property/accessExternalDTD'
Error converting: Error converting SPDX file: class org.apache.jena.shared.NoWriterForLangException Writer not found: TURTLE