13. Is there a ban on donations from any other source?

Political Parties Act 1994, amended 2015, Section 25.

Donations from charity organizations, religious organisations, donations made in exchange for political advantage, donations made through a middle hand.  Donations from political foundations, corporate entities, associations of persons and from estates which under the statutes, the foundation charter or other dispositions governing the constitution of such entities, and by the actual business conducted by such entities, are exclusively and directly intended for non-profit, charitable or church purposes (Sections 51 to 68 of the German Fiscal Code (Abgabenordnung, AO)" (Section 25 2§ (2)) "donations evidently made in the expectation of, or in return for, some specific financial or political advantage;" (Section 25 2§ (7) "donations solicited by a third party against a fee to be paid by the political party and amounting to more than 25 per cent of the value of the solicited donation." (Section 25 2§ (8)