WASHINGTON — The mortgage industry may be in meltdown, but at least one class of lender appears to be flourishing: Islamic finance companies that offer Muslim home buyers alternative arrangements such as lease-to-own deals so they can avoid making the sort of interest payments that many believe the FHA (HUD0 insures then insures the loan and pays the lender if the borrower defaults on the mortgage. The protection offered by FHA mortgages to lenders allows them to be more liberal with their terms than the prospective homeowner might otherwise obtain.