Here, the "money" is trust and knowledge. You can verify by yourself the code you're using and you can learn by being corrected by others and reading code at the same time. So improve your own projects, and improve projects of people who will read yours.
And that's not all the time a "work for free". Just see the price of a some opensource tools' certificates or the cost of a support.
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We're a place where coders share, stay up-to-date and grow their careers.
Here, the "money" is trust and knowledge. You can verify by yourself the code you're using and you can learn by being corrected by others and reading code at the same time. So improve your own projects, and improve projects of people who will read yours.
And that's not all the time a "work for free". Just see the price of a some opensource tools' certificates or the cost of a support.