The members of Class IV shall hold no other municipal office, position or employment, except that one such member may be a member of the Zoning Board of Adjustment or the Historic Preservation Commission, if any, and one may be a member of the Board of Education. A member of the Environmental Commission who is also a member of the Planning Board as required by N.J.S.A. 40:56A-1 shall be a Class IV Planning Board member unless there be among the Class IV members of the Planning Board a member of the Zoning Board of Adjustment or Historic Preservation Commission and a member of the Board of Education, in which case the member of the Environmental Commission shall be deemed to be a Class II member of the Planning Board. For the purpose of this section, membership on a municipal board or commission whose function is advisory in nature, and the establishment of which is discretionary and not required by statute, shall not be considered the holding of a municipal office. Any member other than a Class I member, after a public hearing if he requests one, may be removed by the governing body for cause.