Does translating a library into another language make it a “derivative work” for the purposes of GPL/LGPL? [closed]

Question

I am currently developing an iPhone application where I would like to use some existing code which is published under the LGPL. Because of the nature of Apple’s App Store the application would not be open source and I will probably charge an amount for it (either $0.99 or $1.99) in order to cover the expanses for publishing in the store. I have studied the LGPL and I know that it allows use of code for proprietary software if you are using it as a library. However, the code in question is written in JavaScript so I would need to convert it into Objective-C, which I believe would make it considered as “derivative work” and I guess that requires that it must be open-sourced (please correct me if I am wrong). So my question is if translating a library into another language makes it “derivative work”, and if so is it enough to open-source just the library, or must the entire application using it be published under LGPL as well?

I also have a sub-question. There exists a previous version of the library which has already been translated into several languages, including Objective-C. However, they were written while the library was released under GPL (which prohibits using it in closed-source software). In the mean time the license was changed to LGPL (for the original JavaScript version), but does this affect the translated versions or are they still pure GPL?

Answer 1

So my question is if translating a library into another language makes it “derivative work”

Yes.

and if so is it enough to open-source just the library, or must the entire application using it be published under LGPL as well?

If it is a good-faith translation (i.e. without any other changes), only the library needs to be open-sourced.

In the mean time the license was changed to LGPL (for the original JavaScript version), but does this affect the translated versions or are they still pure GPL?

Any translation or other derivative work based solely on version X of a software is not affected by the licenses of any other versions of the software, earlier or later. So yes they would still be GPL, unless explicitly changed.

This is not legal advice and I'm not a lawyer.