[License-discuss] step by step interpretation of common permissive licenses

[Massimo Zaniboni]

On 17/01/2017 16:13, Massimo Zaniboni wrote:

> On 17/01/2017 15:31, Kevin Fleming wrote:

> Apache/MIT/GPL specify explicitely how you can relicense derived works:
> * in GPL you mus apply the same GPL license also to derived works
> * in MIT/Apache you can freely relicense the derived work, until you
> cite/credit the original work
>
> BSD and ISC do not specify if/how you can relicense, IMHO their text is
> not so clear.

I didn't considered this: "relicensing" is implicitely permitted by 
Berne Convention [https://en.wikipedia.org/wiki/Berne_Convention], and 
so the license text had no to repeat this.

Suppose a product B with a commercial license, derived from a work A 
released under ISC. When ISC says

"Permission to use, copy, modify, and/or distribute this software for 
any purpose [..]"

every change to A made by B is automatically owned by B author, thanks 
to Berne Convention, and protected by copyright laws. So B can choose to 
license these changes under a commercial license because he is the owner 
of these changes.

The only constraint doing so, it is that B can effectively reuse A work, 
and for doing so it must comply to ISC license:

"[..] provided that the above copyright notice and this permission 
notice appear in all copies."

The meaning of "permission notice appear in all copies" is fair to be 
considered as a notification/credit of A work, and not an application of 
A license terms also to B. Otherwise more strong and explicit statements 
should be used in ISC license for ensuring this.

Recursively, if there is a work C deriving from B, C is using 
(indirectly) the work A, and C is informed of this because it is 
signaled by B, so for reusing (indirectly) the work A, also C must 
signal that it is using A, for following the ISC requirements. This 
without requiring that parts of the ISC license of A are applied totally 
or partially to B license. Maybe this point is a little more controversial.

The same reasoning can be applied to BSD license.

ISC and BSD are permissive because thank to Berne Convention every 
change made to something is owned by the author automatically. So by 
default if I can reuse code A under BSD license, I own the changes 
without the needing that BSD license tell me this, because it is the 
Berne Convention telling me this. Product A must tell me only that I can 
reuse it. Then I can choose in wich license terms I will release the 
changes, because I'm the owner.

Apache, MIT, GPL are still more explicit and self-contained in their 
statements, but now I agree that ISC and BSD are permissive licenses, if 
applied toghether with Berne Convention.

Regards,
Massimo