Explain like I'm five · Law/Policy

What is an Open-Source License?

Open-source licenses, told as a story about the rule tag the student council puts on shared supplies.

Here at the student council, where the school's rules and standards get madecan I just copy this freely?what do I follow when I pass it on?the shared supply box has no rule tag yet

The student council is where the school's rules and standards get made.The shared supply box has no rule tag yet.

I made this! (actually copied it)but there's no credit anywherewithout rules, nobody knows who made it or what to follow

Without a rule tag, each user understands the copy and reshare rules differently.Without rules, nobody knows who made it or what to follow.

Open-source license = the rule tag on shared suppliesfree to use, but only by what the tag says

An open-source license is the rule tag on shared code (the shared supplies).Free to use — but only by what the tag says.

Free to usecopy, modify, redistribute
Always credit itkeep the maker's name
Reshare by the tageach tag's rule differs
Don't claim it as yourscopyright notice stays
PERMISSIVE (MIT, etc.)free to usejust credit the sourcemay keep your modified source closedCOPYLEFT (GPL)free to use toobut when you share a modified copyrecipients must get the source toomixing licenses in one program can clash — always check the combination

Open-source tags come in two broad kinds: permissive and copyleft.Mixing licenses in one program can clash — always check the combination.

break the license, and you can lose the right to use the codea parts list tracks which tags got mixed ina license has legal force — an SBOM parts list tracks which licenses got mixed in

The license tag has legal force.Break the license, and you can lose the right to use the code. An SBOM parts list tracks which licenses got mixed in.

In one breath

Open-source license = the rule tag on shared code (the shared supplies). Free to use, but you must credit the source and follow the tag's rule when you pass it on.

Open-source licenses are legal terms governing how source code may be used, modified, and redistributed. They range from lightweight 'permissive' licenses like MIT/BSD/Apache to 'copyleft' licenses like GPL, which require modified versions, when distributed, to come with source under the same terms. Breaking a license can mean legal liability for copyright infringement.

When grown-ups say it

Open Source
Publishing source code so anyone can use and change it. But how free depends on which license.
Copyleft (e.g. GPL)
The tag that says: share a modified version, and recipients must get its source too. Mix it into a program you distribute, and the whole program's source may have to go along.
Permissive License (MIT/BSD/Apache)
The tag that's free as long as you credit it. Safe to mix into closed, proprietary software.
License Compatibility
Whether two different tags can be mixed. Some combinations simply can't be mixed.
Attribution / Notice Obligation
Always writing down who made it. The minimum almost every tag asks for.
SBOM (Software Bill of Materials)
The parts list of which code went in. License tracking is part of it too. → the castle's parts list
Copyright
The original maker's right. Open source doesn't give up copyright — it's still there.
Dual Licensing
Putting both a free tag and a paid tag on the same thing. Use it free under one tag, or pay for different terms.
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