For example, a C repository built upon the ideas from a (say) JavaScript project - is it a derivative work based on the latter?To clear things up little bit, i'd give a more detailed example;Imagine an open source compiler written in JavaScript implements in its code base a high quality code optimization algorithm its authors have discover'd; my question is, can other works, no matter open source or not, incorporate the algorithms in their own code (which might not have been written in the same language as the code whose ideas it is using) and still not be consider'd derivatives (partially at least) of the oiginal work?
Is a derivative work necessarily written in same language as the one it derives from?
derivative works
Algorthms and ideas are not elligible for copyright.As long as it hasn't been patented you can create your own implementation without worrying about copyright (just make sure you copy the algorithm not the code).If you're not sure, contact a lawyer.