From an extensive profile
"If walking away from $850 million feels like penance, Acton has gone further. He has supercharged a small messaging app, Signal, run by a security researcher named Moxie Marlinspike with a mission to put users before profit, giving it $50 million and turning it into a foundation. Now he’s working with the same people who built the opensource encryption protocol that is part of Signal and protects WhatsApp’s 1.5 billion users and that also sits as an option on Facebook Messenger, Microsoft’s Skype and Google’s Allo messenger. Essentially, he’s re-creating WhatsApp in the pure, idealized form it started: free messages and calls, with end-to-end encryption and no obligations to ad platforms.Exclusive: WhatsApp Cofounder Brian Acton Gives The Inside Story On #DeleteFacebook And Why He Left $850 Million Behind -- Forbes
Acton says that Signal now has unspecified “millions” of users, with a goal to make “private communication accessible and ubiquitous.” While Acton’s $50 million should take it a long way—Signal could afford only five full-time engineers until he came along—the foundation wants to figure out a perpetual business model, whether that means taking corporate donations like Wikipedia or partnering with a larger company, as Firefox has done with Google."