On Thursday, April 28, 2016 at 9:21:03 PM UTC-4, 2n wrote: > > If you re-write or translate something doesn't it necessarily mean that > you are no longer using licensed code? that you have full copyrights to the > new code? >
No, typically a translation would be considered a "derived work" of the original work. For a derived work, the copyright is jointly held by both you and the original author, i.e. you need permission from both to distribute (which, in the free/open-source world, you typically get via a license, in this case the LGPL). A re-write is a tricker issue. A "clean room" rewrite, in which the algorithm is re-implemented by someone who hasn't looked at the original code, but has only read the mathematical description of the algorithm, is typically only copyrighted by the new author. However, if you've rewritten after studying the original code, it may be difficult to avoid copying "expressive" elements of the original code that are copyrighted. (Ultimately, there is no deterministic way to know whether something is a derived work of something else -- it can only be determined on a case-by-case basis in a court of law. In practice, people usually assume that if you've studied someone's code and implement something similar then it is probably a derived work.)
