The article notes that the arrangement is a six-month trial that could be expanded. It says:
The A.P. called the arrangement a six-month experiment that could later be broadened to include other investigative nonprofits, and to serve its nonmember clients, which include broadcast and Internet outlets.
The article does not touch on any financial considerations - presumably, the nonprofits would receive no direct compensation for their work - but the enormous visibility that AP distribution offers the nonprofits does create some interesting possibilities as nonprofits seek sustainable business models.
The four nonprofits are: ProPublica, the Center for Investigative Reporting, the Center for Public Integrity, and the Investigative Reporting Workshop.