"OpenStreetMap is the largest open geographic database in the world, the data infrastructure for multitudes of mapping projects around the globe. Your donation to the OpenStreetMap Foundation will cover our core operational expenses in supporting the OpenStreetMap project: hardware costs, legal fees, administrative assistant and other expenses of our working groups and administration.
We currently run extremely lean for an operation for a project the size and importance of OpenStreetMap. The OpenStreetMap Foundation relies on revenue from individual and corporate membership dues, profits generated by the annual State of the Map conferences, and donations. We must keep our income sources diversified, as these vary from year to year, but our modest needs stay the same. For this, we need your support."
(Disclaimer: I'm on the governing board, but derive no financial benefit from it.)