I have been reading up on Open Source licensing, but there is this one term that I think needs clarification.

When is work derivative?

If I have an image viewer that accepts a zip file and I use an open source library under creative commons licensing, then I see two possible interpretations of the terms:

• Adaptations that I make to the zip file library should be shared with the world.
• I need to share my entire application with the world.

Before you answer “copy left owns all” or mark as duplicate, I would like to stress that the point of the question is that the remainder of the application is not attempting to solve a .zip problem. The domain changes. It is assumes that if I have to solve some .zip bugs in the original library, then those bug fixes should should be shared.

For instance, here on stackoverflow, every submitted code is licensed under creative commons license. However, if I have a problem and then get a response containing code, but find that I have to tweak it a bit in order to properly solve the stated problem, I think it would be practical that the “sharealike” caveat be solved by me sharing the end result in the same thread. Not my entire application, but the best possible answer to the problem.

I think clarification of these terms is the key question regarding open source licensing, and I can’t see it addressed anywhere. If I use a matrix transformation math library and I expand upon it and then use it in a biology categorization algorithm, I would say that my extension to the matrix library is “building upon”/”derivative” work (and subject to licensing terms), whereas the biology code isn’t.

Have I missed somewhere where this specific question has been addressed?