Can I enhance one LGPL library based of implementation of another? [closed]

Question

I was wondering if it was legal/not frowned upon to base enhancements to one LGPL library off of the functionality of another LGPL library. Note that because of the method of implementation, the source code could not be directly built off of, however the general idea is to essentially implement similar functionality in another library based off of the functionality in the original library, without copying the implementation or directly using the other library.

An example of what I'm thinking of is:

Both libraries are covered by the LGPL:

Library 1 has function A, and I would like to implement similar functionality to Library 1's function A in Library 2.

Would there be any legal issues with this if I were to indirectly (however still possibly basing algorithms of of the original library) implement similar functionality in this manner?

I do intend on if this is not a legal problem asking the authors of the original library for permission before doing anything, however I want to confirm if what I have in mind is even legal/kosher to do according to the licensing before actually asking.

Sorry if this seems like it may be a little out of place, or a little like I didn't properly comprehend the LGPL, however I really am not good at understanding legal documents, and I was wondering if anyone else had any knowledge of this as well. If nothing else, I may contact the FSF and possibly the EFF seeking advise on this as well.

Answer 1

No license can make it illegal to implement a function with your own code. GPL projects base their code off other implementations regularly such as GCJ (java compiler) and the free Flash player. I could not imagine any GPL'ers getting offended by creating a library with similar functionality.

A patent on the other hand is a different story - protecting the idea behind the code. Perhaps, that is what you are thinking of. Copyright protects that particular instance of code.

If you link to their library then you would have to abide their license. Furthermore, GPL projects can be derived and longs as you keep the license. So you could directly link to their library if you wanted to - just keep the same license for your project.

Answer 2

I'm no legal expert but I don't see any issues with this. The LGPL specifically allows you to modify and redistribute the code as long as the code retains the LGPL license. Combining two LPGL codebases should be no different that using them separately - except that they conveniently share the same license.