On November 16th, Meredith Whittaker, President of Signal, published a detailed breakdown of the popular encrypted messaging app’s running costs for the very first time. The unprecedented disclosure’s motivation was simple - the platform is rapidly running out of money, and in dire need of donations to stay afloat. Unmentioned by Whittaker, this budget shortfall results in large part due to the US intelligence community, which lavishly financed Signal’s creation and maintenance over several years, severing its support for the app.
OTF funding is also not a direct indication of funding from US intelligence or backdoors in the code. OTF could just be promoting development of software that breaks free of repressive regimes, which indirectly benefits US foreign policy.
See the last part of my response to this article for one of the other ways it benefits the US.