Thinking further on the whole "what is derivation" issue I have been discussing with Brian Mastenbrook (here, here, here and here).

After some thinking (and essay writing), I think the main contention is "is the copyright on the source, on the executable or on both".

Clearly, if the copyright covers the executable program, it will be incorporating the object library it links to and thus, at all instances of actually running, be a derived work.

Likewise, if the copyright is on the source code, it will only be referencing the library and thus ends up in a similar position to a critique, referencing well-chosen sections of another work.