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Yes, if you link to a GPL'd library your program must also be GPL'd. That is why the LGPL was created. Only example that immediately jumps to mind. Edit: reph

Yes, if you link to a GPL'd library your program must also be GPL'd. That is why the LGPL was created. Only example that immediately jumps to mind. Edit: rephrased for clarity

Dylan16807 13y ago
Don't they claim that the linking rule works via derivation? As far as I understand it, the FSF would tell you that anything linked is always derivative. But that doesn't mean it's true. If you could prove that a particular instance of linking to a library was not derivative, would they still claim your program had to be GPL? As I understand it, the LGPL exists to 1. provide legal certainty and 2. allow some amount of external derivation if necessary. And it's easy to create an artificial dynamic-linking case where there is provably no derivation, using multiple libraries with the same API.
- rgbrenner 13y ago
  Don't they claim that the linking rule works via derivation? Yes.. it was the closest thing I could think of where the two pieces of software are fairly separated. I mean you could have a huge proprietary program, and a developer calls gsl_pow_int() from the GNU scientific library, and the entire program must be licensed under the GPL. I think that's about as close as you're going to get. If you're looking for a case where the FSF said a piece of software had to be licensed under the GPL, even though it was NOT a derivative work, I don't think you'll find it. The reason it must be a derivative is copyright law.. the GPL can't unilaterally change that.
  - Dylan16807 13y ago
    The GPL can't extend copyright law, but it can refuse to let you distribute. It's possible to make a license that would say "can't be distributed with other software that does X". But good, I'm glad there's nothing like that in the licenses here that I missed. Just the normal derivation-based questions.
    - rgbrenner 13y ago
      Yes, you are right.. I didn't think of that case.. They cover this question in the FSF GPL faq: http://www.gnu.org/licenses/gpl-faq.html#MereAggregation http://www.gnu.org/licenses/gpl-faq.html#MereAggregation And they do have a requirement if you do so: The only condition is that you cannot release the aggregate under a license that prohibits users from exercising rights that each program's individual license would grant them.

Yes, if you link to a GPL'd library your program must also be GPL'd. That is why the LGPL was created. Only example that immediately jumps to mind. Edit: rephrased for clarity

Dylan16807 13y ago

Don't they claim that the linking rule works via derivation? As far as I understand it, the FSF would tell you that anything linked is always derivative. But that doesn't mean it's true. If you could prove that a particular instance of linking to a library was not derivative, would they still claim your program had to be GPL? As I understand it, the LGPL exists to 1. provide legal certainty and 2. allow some amount of external derivation if necessary. And it's easy to create an artificial dynamic-linking case where there is provably no derivation, using multiple libraries with the same API.

rgbrenner 13y ago
Don't they claim that the linking rule works via derivation? Yes.. it was the closest thing I could think of where the two pieces of software are fairly separated. I mean you could have a huge proprietary program, and a developer calls gsl_pow_int() from the GNU scientific library, and the entire program must be licensed under the GPL. I think that's about as close as you're going to get. If you're looking for a case where the FSF said a piece of software had to be licensed under the GPL, even though it was NOT a derivative work, I don't think you'll find it. The reason it must be a derivative is copyright law.. the GPL can't unilaterally change that.
- Dylan16807 13y ago
  The GPL can't extend copyright law, but it can refuse to let you distribute. It's possible to make a license that would say "can't be distributed with other software that does X". But good, I'm glad there's nothing like that in the licenses here that I missed. Just the normal derivation-based questions.
  - rgbrenner 13y ago
    Yes, you are right.. I didn't think of that case.. They cover this question in the FSF GPL faq: http://www.gnu.org/licenses/gpl-faq.html#MereAggregation http://www.gnu.org/licenses/gpl-faq.html#MereAggregation And they do have a requirement if you do so: The only condition is that you cannot release the aggregate under a license that prohibits users from exercising rights that each program's individual license would grant them.