Evaggelos Balaskas wrote:
I don't know about that age (3-12) but one of the classics in that area (my opinion) is The Cathedral and the Bazaar by Eric S. Raymond
That essay focuses on developmental methodology and business interests ("...and listen to your customers", case reviews on businesses like Netscape). Free software focuses on ethically of treating other people with regard to computers; free software isn't anti-business but the free software movement doesn't give primacy to business interests. These different philophies reach radically different ends when comparing the reaction to reliable, featureful proprietary software (as https://www.gnu.org/philosophy/open-source-misses-the-point.html describes toward the end).
Raymond's essay refers to "Linux" as an operating system (or outright claims "the Linux operating system") despite that Linux is and was a kernel.
For free software rationale I recommend the material on https://audio-video.gnu.org/, the collected rms essays in "Free Software, Free Society", and asking rms directly by emailing rms@gnu.org.