The ads are powered by a new project called Funding, authored by one of the Standard devs. The Funding library was included with the Standard 14.0.0 release, published last week, when the ads first started showing up in other people's terminals.
The idea behind Funding is that companies buy ad space in people's terminals, and the Funding project then shares its profits with open-source projects who signed-up to show the ads.
Terminal is the last place where I expected to see ads. It is so sad they finally penetrated this impregnable fortress.