BRIDGEWATER — A plan to build affordable housing on Main Street North — in the works for the last 20 years —hit another roadblock this month when a state judge declined to enforce his own 2003 ruling. In an eight-page decision, Judge Trial Referee William Mottolese agreed with the town’s Planning and Zoning Commission that the project, which started out as a 35-unit development and would now have 100 apartments instead, had changed too much to be considered the same one he ordered the town to accept 15 years ago.