PNML 2 dot is distributed as a jar, ready to be used on command line or as a library in your application for whatever purpose. It runs on Java 1.6 only.
You can download it from this link.
If you are an Eclipse user and want to use it as a dependency, you can download it using the update manager. In this case, point it to http://pnml.lip6.fr/pnml2dot/UpdateSite/.
Usage information is here.
Download the latest zip archive of PNML Framework (which contains its own dependencies), args4j, and put them together in a lib directory so that you have the following folder structure:
Up to now, PNML Framework depends on lpgjavaruntime_1.1.0.v200711021030. You will find its jar among PNML Framework downloaded dependencies (see above). You are advised to replace that jar with this new one.