Okay, before everyone goes shouting about duplicate questions, yes, I've already seen several questions like this here. But none answer the question.
If I link against a GPL-ed library without modifying that library, do I need to release my source code?
According to this question, the answer is yes!
But this answer is not satisfactory to me. The answer basically says that I cannot use GPL code in any way without making my code open source.
But if the previous is true then that would indicate that no person or organization could ever release any proprietary software on Linux ever. Which must be wrong. Simply because in order for any application to do anything useful, open files, write to the console, create TCP connections, the application must be linked to libc which is GPL-ed.
So my question is this: If the GPL states, as all the previous answers on the site say it does, that a program which links to another GPL program must be GPL itself, how is it possible to create/release/sell any proprietary application at all which runs on Linux? Since as I described above that application must be liked to GPL code just to run on Linux.
A more practical example say I link to a shared library which is GPL-ed in a non-GPL application, would that force the non-GPL application to become GPL-ed? More specifically if I use a GPL library without modifying it, and then distribute that library as an .so or .dll, would that require my application be open source?
Best Answer
If you link to a GPL lib then you have created a derived work and your code must be GPL - this is different to LGPL code which specifically allows dynamic linking of differently licensed code. The system libraries including libc, are all LGPL.
There is also a special exemption for the Linux kernel headers and libgcc (the library implicitly called to by the compiler).