Does a GPL API infect its apps?

[Ken Arromdee]

On Thu, 21 Oct 1999, Ross N. Williams wrote:
> I just want to point out that the use of the virus metaphor to describe
> the legalities of association in relation to the GPL is inappropriate
> because the "infection" does not proceed beyond one level.
>    GNU GPL V2: 2.
>    These requirements apply to the modified work as a whole.  If
>    identifiable sections of that work are not derived from the Program,
>    and can be reasonably considered independent and separate works in
>    themselves, then this License, and its terms, do not apply to those
>    sections when you distribute them as separate works.  But when you
>    distribute the same sections as part of a whole which is a work based
>    on the Program, the distribution of the whole must be on the terms of
>    this License, whose permissions for other licensees extend to the
>    entire whole, and thus to each and every part regardless of who wrote it.

That seems to keep it from proceeding beyond one level, but really, it doesn't.
In fact, it does nothing at all.

Suppose I add a function to a GPL program.  Someone else wants to use the
function--only the part I added, nothing from the original GPL program--with
their own code.

The GPL says that my added function must be GPL when it is distributed as part
of a GPL program.  Once it becomes GPL, it stays GPL--the GPL doesn't contain
any clause saying that the function once again becomes non-GPL after it is
removed from the program.

This causes the virus effect, since the other person who is using my function
must place their code under GPL.  They would have to go directly to me in order
to get a non-GPL copy of the function, even though that copy is byte-for-byte
the same as the copy they snarfed from the program.

Here's a hypothetical version which does not have this problem:

>But when you
>distribute the same sections as part of a whole which is a work based
>on the Program, the distribution of the whole must be on the terms of
>this License or a license which grants permissions which are identical to this
>License except for the possible addition of extra permissions on the sections
>which are identifiable works as described above.