Section 5 of chapter 40A of the General Laws, as appearing in the 2016 Official Edition, is hereby amended by inserting after the word “members”, in line 90, the following words:- ; provided however, that any adoption of, or amendment to, a zoning ordinance or by-law to allow for inclusionary zoning may be passed by majority vote. As used in this paragraph the term “inclusionary zoning” shall mean a residential subdivision or a multi-unit residential project of a size to be determined by the municipality; and provided further, that a certain percentage of such subdivision or project’s dwelling units or net floor area, as determined by the municipality, shall be reserved for the construction of dwelling units permanently affordable for occupancy to persons whose household income does not exceed a municipally determined per cent of such municipality’s area median income as such income is determined by the federal department of Housing and Urban Development.