1.) javaws and jnlp has pretty much always required the full non-free JRE, I
don't think it was ever a thought to package a Java Web Start application in
main, much less develop guidelines for it.
2.) Java Web Start and jnlp have had marginal adoption over the years and are
considered passé by most Java developers I know and work with. Is there a
particular Java Web Start application you had in mind?
3.) Does OpenJDK fully support javaws/jnlp, and in particular the application(s)
being considered for packaging? If not, bear in mind that these packages will
always live in non-free if they require the official Oracle JDK.