It's more like building a neighborhood from scratch, taking care of it for fifteen years, and then seeing the ones you handed it over to being bought by the ones who owns the rest of the city.

I don't get where people get this strange attitude from. Like you're more of a "sellout" when you build a company over time, with an open source product and don't want to be controlled by your competitor. Than if you, like most startups today, build a proprietary product with the intention of selling to you biggest competitor as soon as possible.