The plugin doesn't obfuscate JARs but it can deploy JARs that have already been obfuscated.
One approach would be to use the proguard-maven-plugin to obfuscate the JARs and the build-helper-maven-plugin to attach the obfuscated artifact to the project along with the unobfuscated JAR and install them both in your local repository. Then when you configure the Webstart Plugin with the dependencies to be deployed in your JNLP bundle, you can choose between the obfuscated or unobfuscated JARs.
The servlet cannot yet be found on an central Maven repository. For demonstration purposes, the webstart project packages one version under the (currently) following identifiers
<groupId>org.codehaus.mojo.webstart-maven-plugin</groupId> <!--groupId>com.sun.java.jnlp</groupId--> <artifactId>jnlp-servlet</artifactId> <version>1.0-6.0-02_ea_b02-SNAPSHOT</version>