@mangeurdenuage As a non-profit organization, there are forms filed with the IRS (federal tax collection agency) and with at least one state government, so the information is available. But remember that almost all of their work is done by volunteer contributors.

Also, as @sl points out, a little scarcity of funds breeds care in spending. If for no other reason than forcing choices earlier. Google is an example. At any time, they have 2-3 messaging platforms ... and a couple of others being developed. Every few years, they kill off the released platforms and launch a couple of replacements. If they were money-constrained, they would be forced to choose one and give it their full attention.