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."

https://telegram.org/faq#q-how-are-you-going-to-make-money-o...

This is actually really awesome. I know telegram received a lot of flak for their bold security claims, but it really is a fantastic messenger. It's the best I've used that's available in the app store aside from Facebook's.

In practice there would be no good way to make it legally binding. Even defining what you mean by "selling out" would be incredibly difficult in plain English let alone codifying it in legalese.

I don't think you can trust an organization anymore than you can "trust" a weapon. A bad person could theoretically take control of it and use it for evil.

The closest you can get is trusting the individual at the helm. You know Automattic isn't going to do anything weird as long as Matt Mullenweg is the dictator.

I wouldn't mind so much for "legal". If a company is owned by someone who is incredibly rich (and this person wants to be in there for the fun), it won't be for sale. This person can end up under a bus of course, so I don't know to whom you want to promise this. :-)

Using that criterion the immediate example is Craigslist.

Closest company I've heard that does it is posthaven.com

Granted, there's nothing legally binding. But it's one of their selling points.

Thanks, this is an example of what I was looking for. We are an independent scientific publisher (thewinnower.com) and we want to ensure our users that we will not give over control to giants like Elsevier or Sage, should we ever get to that point. Kind of like Mendeley and Elsevier(http://www.newyorker.com/online/blogs/elements/2013/04/elsev...)