Since emf2gv 1.0.4, it is possible to generate diagrams with emf2gv outside of Eclipse.
Once the Graphical Description have been produced (in an Eclipse environment), it can be used in a standalone application (or a J2EE application) to generate diagrams through a simple API through the org.emftools.emf2gv.processor.core.StandaloneProcessor
class.
A tutorial can be found here.