It’s been 35+ years since I read a case in law school on “legal standing”, but I believe any plaintiff would have to be a citizen. Unfortunately, Free Republic is not a citizen.
Standing takes more than just being a citizen, it takes a demonstration of injury. So basically the only people with standing are candidates and electors, which is who is filing as far as I can tell.
Nobody else probably remembers this, but there was a lawsuit before the Electoral College voted in 2000 claiming Bush and Cheney both lived in Texas, so the Electoral College couldn’t vote for both of them. The Court refused to hear it on standing grounds, and also commented that separation of powers kept them from enforcing Constitutional requirements on the EC; the EC is ultimately its own judge.
And, to be frank, in 8 years this whole birth certificate stuff will probably be as forgotten as that case is now.