This should at least be signed with a valid certificate, preferably not self signed…
Just stumbled into this 
We don’t have one.
Being of the inclination that “official” CAs are a bunch of ***oles I’d rather trust a certificate signed by jMonkeyEngine. Actually, it would be pretty good if jMonkeyEngine could have a (self signed) root certificate that could be used to issue signer certificates for the contribution plugins. Is it possible to add trusted CA certs to netbeans?
You should be able to just reference the file yeah.
LWJGL have a valid certificate and they also have a “JNLP extension” that you can include in your webstart app to have LWJGL fully working with natives and such.
The demos on the jME3 site are from like 1 year ago, if not more. Perhaps they should be updated …