Open Source Is About the License, Not the Price

People use "open source" to mean free, or "the code is on GitHub," or just vaguely good and community-minded. Those overlap with the real meaning, but none of them is it.

Open source software is software whose license gives you the right to use it for any purpose, read the source code, change it, and share it, including your changed version. The Open Source Initiative keeps the formal definition and a list of licenses that meet it. The key word is rights. It's not about whether you can see the code. It's about what you're legally allowed to do with it.

That distinction matters more than it sounds. Plenty of projects put their code in a public repository with a license that says you can look but not run it commercially, or not offer it as a hosted service, or not modify it. That's usually called "source available." It might be a perfectly fair business decision, but it isn't open source, and it doesn't give you the same guarantees. Code with no license at all is the strictest case: by default, the author keeps all rights, and you technically can't reuse it.

The old phrase people use for this is "free as in freedom, not free as in beer." Most open source software happens to cost nothing, but nothing in the definition says it has to. Companies sell support, hosting, and extra features around open source projects all the time. Red Hat built an entire business on it.

Within open source, licenses come in two broad flavors.

Permissive licenses, like MIT, BSD and Apache 2.0, let you do almost anything, including folding the code into a closed, commercial product. Mostly they just ask you to keep the copyright notice.

Copyleft licenses, like the GPL, say that if you distribute a modified version, you have to share your changes under the same license. That's what keeps improvements flowing back to everyone. The AGPL extends that to software you run as a network service, which is why you see it on a lot of self-hostable web apps.

Neither style is better. They reflect different priorities.

One myth I'd push back on: that open source is automatically more secure because "anyone can read the code." Anyone can, but that doesn't mean anyone did. Well-maintained open source projects with active reviewers are in great shape. A small library maintained by one tired volunteer may have had almost no eyes on it at all. What open source does give you is the ability to check, or to have someone check, and to fix it yourself if the maintainer disappears. That's real value. It's just not the same as a guarantee.

If you're about to build on a project, or self-host one, open the LICENSE file before anything else. It's usually short, and it tells you more about what you can do than the README ever will.