Well I'm still fuzzy about who is excluded. Do Mormons consider themselves trinitarians? I would think "non-denominational" would exclude methodists, catholics, lutherans, presbeterians(sp) and such. I go to a Plymoth Brethren which certainly considers itself non-denominational.
Im of the opinion that anyone who holds a Trinitarian doctrine, and does not belong to a denom should be allowed to participate.
Plymouth Brethren are welcome (Im close friends with one fyi).
All we ask is that if you are not a member of the ping list (which you have joined), a poster presently with an organized denomination ask permission before participating, consistent with caucus rules.