Pro-am theatre started in Australia, more specifically in Adelaide in 1984, where it is still going strong. So far, to the writers' knowledge no famous actors have come from pro-am, though famous people have performed in pro-am.
Not only does this type of theatre encourage amateurs it allows unpaid professionals somewhere to practice the talent before they find work. Recordings of unpaid professionals doing such a piece doesn't usually count as a professional piece of work, at least not by current equity rules.
Exactly what this Pro-am Theatre is and what it will become has yet to be established. However this may be considered a technical description for this type of drama.
However given the growth of Repertory, Theatre in Education, Footlights and Fringe Theatre in the UK (Off-Off Broadway in America) and their impact on mainstream drama the impact of Community Theatre cannot be underestimated.