The company is paying the people working by providing a free service. It's like youtube. Youtube provides a free hosting of your videos. In exchange they monet

The company is paying the people working by providing a free service. It's like youtube. Youtube provides a free hosting of your videos. In exchange they monetize them. You're free to host them on your own servers. That will likely cost you way more than putting them on youtube. So you're getting something from them. You're also getting their advertising service to monetize your videos. You could do it yourself, hire a bunch of people and try to get companies to put ads on your self-hosted videos. Again, unless you're wildly successful it's unlikely you'll be able to do that and make a profit. So, youtube is effectively paying you. Same with Stack Overflow. They're providing the servers, the bandwidth, etc. It costs them $. They're providing that service to you.