(on plaintiff's motion for summary judgment that income from its "extracurricular" activities are not subject to unrelated business income tax court ruled that brokerage services income and commissions are tax-exempt when earned from member activity, but is subject to UBIT when earned from non-member activity with no deminimis exception; UBIT applicable to 4 percent interest that credit union owned in a partnership consisting of a group of credit unions; case remanded for trial on whether income related to credit life and disability insurance products subject to UBIT).