Yet I'm blocked from joining, unless I subscribe? Were they grandfathered in as the site grew in popularity? Just curious. Great site, by the way!

Those nonsubs were subs who cancelled their subscription or had it run out on them.

RHP allows them to finish all the games that the started, but the cannot take on extra games until the are below the limit for nonsubs (6 games).

They should drop off the ladder once they finish their current ladder game.