I contributed financially by
1) joining the Foundation and paying annual dues
2) buying the Firebird book from the Foundation where it costs me more than
from other sources but brings in minimal income to the Foundation

As an individual who does not have a business that benefits from FB, I
can't do much more. But I also support Firebird and the Foundation by
talking about it whenever a DB choice is being discussed.

Here's an idea: Every business that places an FB copy into a client
location buys a copy of the Firebird book from the Foundation and leaves it
with the client. Tell them its technical documentation that you want them
to have in case they ever need it. If you deliver strictly embedded, hidden
DB then buy the book anyway and donate it to your local library and then
factor in the cost to the sale.