This requirement shall apply beginning with the effective date of this article to any multifamily or single-family attached residential development, including the residential portion of a mixed-use project, which consists of five or more new residential units at a density of six dwelling units or more per acre, whether permitted by a zoning amendment, a use variance granted by the Borough's Planning Board acting as a Board of Adjustment, or adoption of a redevelopment plan or amended redevelopment plan in areas in need of redevelopment or rehabilitation.