Suppose you wanted to do what some code does, then you see this LGPL code. What can you do? Adjust variable names and play with line spacing and comments until it feels different?
First off, that's a library of pedagogical implementations, so I wouldn't even want to copy it -- I'd prefer a library focused on performance. Second, it's linear algebra, there are alternative implementations and libraries out there. Third, it's covered by the LGPL, so I'd be perfectly happy to link to the library. Fourth, I'd look up a pseudocode description and go from there. In no case would I sit down with another person's implementation and give it the undergrad treatment to pretend that I'm not copying.
"In computer programs, concerns for efficiency may limit the possible ways to achieve a particular function, making a particular expression necessary to achieving the idea. In this case, the expression is not protected by copyright."
So if it's fine to copy the pseudocode implementation of a non public use codebase, then you couldn't possibly object to recreating a codebase into a different language then, right?
But I don't care about the expression of the idea. I just want the idea to work. And I don't know how to do the idea myself. And I've seen how you've done it.
If I want to describe life with a nature metaphor, and then see you do it with a waterfall, I can probably get away with using a waterfall to the same metaphorical effect in my story.
