Whatsapp competitor Telegram is promising that. Not sure if it's legally binding though. (They're also saying that they're not "commercial company").
"Telegram is not intended to bring revenue, it will never sell ads or accept outside investment. It also cannot be sold. We're not building a “user base”, we are building a messenger for the people."
"Telegram is not intended to bring revenue, it will never sell ads or accept outside investment. It also cannot be sold. We're not building a “user base”, we are building a messenger for the people."
https://telegram.org/faq#q-how-are-you-going-to-make-money-o...