How to earn money through open source software?

I know all the positives of open source software, but what I am asking is this. Is it possible to make money out of it? If yes, how?

If it isn't possible, then can we hope for a future where all software will be open source? I doubt there will be many people wanting to "work" for free. Would it attract less people to software development? How will it affect software companies?

Lots of ways to make money on open source software .
The most common ways are to sign up to a list and adding ads for software for you to buy.
There are many more such as making tutorials or upgrading to pro, only limited by imagination

One common way to make money off open source software is to charge for support. The product itself is free, but support contracts are not.

The best ways to make money with open source software is though paid support, consulting and customization. There are lots of companies as well as individual consultants that make a living this way.