The income received and due to the institutions of the university system from all other sources, including bequests, trusts, income from bequests and trusts, student fees and tuition charges, rents, sales, and any other income, from whatever source derived for the institutions of the university system, shall be retained by the treasurer of the university system and be used in such manner as the trustees may determine or as is provided by law or by the conditions incident to trusts, gifts, or bequests.