(1) An association, trust or other unincorporated organization that is taxable as a corporation for federal income tax purposes is not subject to tax under this chapter, but is taxable as a corporation under ORS chapter 317 or 318, or both, as provided therein.
(2) An association, trust or other unincorporated organization that is not taxable as a corporation for federal income tax purposes but by reason of its purposes or activities is exempt from federal income tax except with respect to its unrelated business taxable income, is taxable under this chapter on such federally taxable income.