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Comment by alwayslikethis | Hacker News Reader

My understanding is that permissive licenses (BSD,MIT) can generally be relicensed. For example you can fork a MIT project under GPL. But to do the same for a GPL project requires agreeement from all copyright owners, or just you if you made everyone sign a CLA. This is the whole point of GPL.

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Your general understanding is wrong, as there's nothing in either BSD or MIT that allows for re-licensing, and nothing else gives you that right.

You can incorporate MIT/BSD code in a proprietary project, but that imported code itself remains BSD/MIT licensed. For many projects, this is a technicality, but no, you can't claim copyright on MIT/BSD code that isn't yours.

>as there's nothing in either BSD or MIT that allows for re-licensing

But also nothing preventing you from doing it.

MIT can be relicensed, for sure.

Of course not. What makes you believe that?

The MIT license is not very long, and it contains this sentence:

> The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

Which clearly state that you can't remove that license to put your own.

> What makes you believe that?

Probably the sublicense wording that many techies confuse with relicensing.

Also sloppy wording in discussions like HN where "relicense" is sometimes used as a shortcut for "combined with a compatibly-licensed work in a larger work that can be used under the whole-work license".

If you're the sole copyright owner, of course you can.

That is not the case with other licenses.

No, it cannot. You can incorporate an MIT licensed work into a work that is licensed differently, but compatibly (not a real problem with MIT), but now you have three works that are under different licenses: the MIT part, the "other" part and the whole. The MIT part stays MIT. Someone can cherry-pick just that file (or file snippet) and use it under MIT, without caring about the license of the whole.

What happens when a file was previously under MIT, the license changes, and a new change is made? Do I need to look at the git blame to find which parts I can use as MIT?

You don't need blame necessarily, just git log. You look at the latest version under your preferred license. That's the one you take your snippets from.

Technically your statement is incorrect. The MIT license allows dealing without restriction and sub-licensing, but the effect of re-licensing an MIT product as GPL would be a license with many unenforceable terms on the code that is MIT licensed.

> Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

> The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

Note the "deal in the Software without restriction" and "sublicense" permissions and the virality of the terms that require the permission notice must be included with all copies.

One problem with this however is if someone has removed the license from the software like what has happened here, then that software really has no license because the license doesn't specifically state that it applies to derivatives. The Apache 2.0 license is much clearer on that subject of derivative works.

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