The county’s original dream of converting the former San Geronimo Golf Course into open space has been brought to fruition: The Marin Open Space Trust is purchasing a conservation easement from the property owner, ensuring that the land will not be developed. The $3.2 million deal covers 135 acres of the 157-acre property, which is owned by the Trust for Public Land and is now named the San Geronimo Commons. “We see it as a…