At least in the USA, the copying of a program you legally received into working memory doesn't require a license of any kind, it is a type of fair use. I believe the EU has an explicit exception to copyright for the same reason. So I don't think any problem would arise when running the programs.
The only pertinent question is whether a program B designed to require library A is a derived work of library A or not - and this is a question for the copyright courts, the license of library A has nothing to say about this.
Now, I think even if it were established that program B is not a derived work of library A, it could be possible for library A to have a license that says "you're not allowed to distribute this library to others unless both you and they agree to never link program B or works derived from it with library A". The GPL could be modified to say something like this, and it may still match its original goals - though it may be more difficult to litigate this type of license term (in many countries, license or contract terms can be declared too onerous and be ignored).
> At least in the USA, the copying of a program you legally received into working memory doesn't require a license of any kind, it is a type of fair use. I believe the EU has an explicit exception to copyright for the same reason. So I don't think any problem would arise when running the programs.
My point wasn't about copying into memory being a license violation, rather the fact that you're combining two works together into a single program that violates the license of one of the works. Who is liable for the violation in that case? The user who combined the works together or the developer who created a program that instructs the user to combine those works together?
Perhaps you're selling a book that's derivative of Stephen King's novels, but instead of actually including text from his novels you insert pages that just say "insert chapter 5 from the Shawshank Redemption here". Even though it contains instructions to create a derivative work, it is not in itself a derivative work.
However if the reader follows those instructions and creates a completed work by inserting those chapters as instructed. That completed work definitely is a derivative work of Stephen King's novels.
In the case of computer programs, but not Stephen King novels, in the US there is 17 USC 117 to consider which includes this:
> (a) Making of Additional Copy or Adaptation by Owner of Copy.—Notwithstanding the provisions of section 106, it is not an infringement for the owner of a copy of a computer program to make or authorize the making of another copy or adaptation of that computer program provided:
> (1)that such a new copy or adaptation is created as an essential step in the utilization of the computer program in conjunction with a machine and that it is used in no other manner, or
> (2)that such new copy or adaptation is for archival purposes only and that all archival copies are destroyed in the event that continued possession of the computer program should cease to be rightful.
That should cover most likely scenarios of someone combining programs and/or libraries from various sources on their own computer as long as they own the particular copies of those programs and/or libraries that they are combining.
As a general rule, anything you do with a copyrighted work in private quite possibly falls under fair use, as long as the copies you are using were obtained legally. If you want to write Shawshank Redemption fan-fiction and read it to your kids in bed, even if Stephen King found out and decided to sue you, you're probably covered under fair use. Creating a program just for yourself that uses two separate copyrighted programs (that you obtained legally!) is almost certainly legal - even if it would be completely illegal to distribute that program to others.
This gets murkier if you're using it in a commercial setting, though.
> I think even if it were established that program B is not a derived work of library A
I don't think it ever will be.
> program B designed to require library A
How do you design program B to require A, without inspiration from A?
I believe you can't. For a silly example, take a puzzle peice. To integrate support for your puzzle in my work, I'm gonna have to copy some of your edges.
Onerousness defence can be defeated by anti-severability clauses, if that clause is written to require full reversal of performance in case of termination.
The only pertinent question is whether a program B designed to require library A is a derived work of library A or not - and this is a question for the copyright courts, the license of library A has nothing to say about this.
Now, I think even if it were established that program B is not a derived work of library A, it could be possible for library A to have a license that says "you're not allowed to distribute this library to others unless both you and they agree to never link program B or works derived from it with library A". The GPL could be modified to say something like this, and it may still match its original goals - though it may be more difficult to litigate this type of license term (in many countries, license or contract terms can be declared too onerous and be ignored).