[Ezhik]

To my knowledge most models of making a profit with open source involve selling services like support or hosting around it.

The value of Red Hat is also in support and training that they offer.

So I think big companies can exist with open source easily, and they already do. I do, however, have questions about what a single developer can do. Can't really offer a whole lot of support for some widget you'd normally sell in an app store.