Yes, I'm placing the contents, not the folder itself, into the jar.
Thanks. I'm trying it out so far and it has launched correctly once and generated a new world.
Also, I've noticed with other forge server installations that you use the forge universal download file, which is a .zip file, and change the ending to .jar. Then, opening forge.jar launch minecraft_server.jar on forge. I haven't yet tried this with Voltz, but it worked fine with the Divine RPG server I made.
Maybe they could modify the "PUT IN minecraft_server.jar" folder so that in the future, it will be named Voltz.jar and will launch the server...