The Old Federal Courthouse in Downtown has languished unoccupied for about 10 years now. Last year, a team of consultants advised the city to do something with the property, warning that it had become a “monument of indecision” — words now stenciled in polite graffiti on the courthouse door. Now, five groups have thrown their hats into the ring to redevelop it, responding to the city’s call for credentials. The projects and players range in ambition and notoriety. One idea would add 135 new residences to the district. Below are the responses and some overviews.