The Firebird Foundation (FF) is the organization behind Firebird that actually pays for the salaries of the core developers. FF gets its money from associations, donations and sponsorship. Anyone can become a member of the FF (USD 50/year for non voting member, and USD 300/year for voting member) and every member of the FF are eligible for special discounts from several partners, like IBSurgeon, FastReports, Upscene, etc. A list of companies offering special discounts to the FF members can be seen at http://www.firebirdsql.org/en/member-to-member-offers/.
So, what are you waiting for? Enjoy your discount, and if you are not still a FF member, apply for your membership now!