So, this site costs money: is there a way to give a charitable donation for the purposes of the site?

Booru.org fronts all the cost of running this and every booru site under their banner. They pay for it with advertisements that are run on every booru. So, no, not really.

But keep that idea, because we may be approaching a situation where we could use donations.

Yeah, if we can ever get the software working! XD