consider there's application jars under /var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/testBundlerWorkDir/jars

We're passing copyright through -Bcopyright=<...> and trying to bundle dmg.

Running command :
"/Library/Java/JavaVirtualMachines/jdk1.8.0.jdk/Contents/Home/bin/javafxpackager" "-deploy" "-verbose" "-outdir" "/var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/testBundlerWorkDir" "-outfile" "test" "-native" "dmg" "-BfxPackaging=true" "-BmainJar=/var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/testBundlerWorkDir/jars/testFxAppWithUtil.jar" "-Bclasspath=/var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/testBundlerWorkDir/jars/Util.jar:/var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/testBundlerWorkDir/jars/testFxAppWithUtil.jar" "-srcfiles" "/var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/testBundlerWorkDir/jars/Util.jar:/var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/testBundlerWorkDir/jars/testFxAppWithUtil.jar" "-appclass" "testapp.App1" "-Bidentifier=IDENTIFIER" "-BlicenseType=SQE GPL v.100.500" "-Bcopyright=Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved." "-srcdir" "/var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/testBundlerWorkDir/jars"
[STDOUT]: Using base JDK at: /Library/Java/JavaVirtualMachines/jdk1.8.0.jdk
[STDOUT]: Looking for bundlers for type=INSTALLER format=dmg
[STDOUT]: Building DMG package for null
[STDOUT]: Preparing Info.plist: /var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/build3338737893077845810.fxbundler/macosx/Info.plist
[STDOUT]: Using default package resource [Bundle config file] (add package/macosx/Info.plist to the class path to customize)
[STDOUT]: Using default package resource [icon] (add package/macosx/null.icns to the class path to customize)
[STDOUT]: Config files are saved to /var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/build3338737893077845810.fxbundler/macosx. Use them to customize package.
[STDOUT]: Using default package resource [dmg background] (add package/macosx/null-background.png to the class path to customize)
[STDOUT]: Using default package resource [volume icon] (add package/macosx/null-volume.icns to the class path to customize)
[STDOUT]: Using default package resource [script to run after application image is populated] (add package/macosx/null-post-image.sh to the class path to customize)
[STDOUT]: Preparing dmg setup: /var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/build3338737893077845810.fxbundler/macosx/null-dmg-setup.scpt
[STDOUT]: Using default package resource [DMG setup script] (add package/macosx/null-dmg-setup.scpt to the class path to customize)
[STDOUT]: Creating DMG file: /var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/testBundlerWorkDir/bundles/null.dmg
[STDOUT]: Running [/usr/bin/hdiutil, create, -quiet, -srcfolder, /var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/build3338737893077845810.fxbundler/images/dmg.image, -volname, null, -ov, /var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/build3338737893077845810.fxbundler/images/null-tmp.dmg, -format, UDRW]
[STDOUT]: Config files are saved to /var/folders/z1/735zmdc529g9zxnwpfflz6_w0000gn/T/build3338737893077845810.fxbundler/macosx. Use them to customize package.
[STDERR]: Exception in thread "main" java.lang.NullPointerException
[STDERR]: at java.lang.ProcessBuilder.start(ProcessBuilder.java:1012)
[STDERR]: at com.sun.javafx.tools.packager.bundlers.IOUtils.exec(IOUtils.java:140)
[STDERR]: at com.sun.javafx.tools.packager.bundlers.IOUtils.exec(IOUtils.java:132)
[STDERR]: at com.sun.javafx.tools.packager.bundlers.IOUtils.exec(IOUtils.java:126)
[STDERR]: at com.sun.javafx.tools.packager.bundlers.MacDMGBundler.buildDMG(MacDMGBundler.java:345)
[STDERR]: at com.sun.javafx.tools.packager.bundlers.MacDMGBundler.bundle(MacDMGBundler.java:101)
[STDERR]: at com.sun.javafx.tools.packager.PackagerLib.generateNativeBundles(PackagerLib.java:524)
[STDERR]: at com.sun.javafx.tools.packager.PackagerLib.generateDeploymentPackages(PackagerLib.java:503)
[STDERR]: at com.sun.javafx.tools.packager.Main.main(Main.java:428)


That's an output we get.
To reproduce, run the mentioned command on Mac OS 10.9