GPL Infectiousness

On Tue, 1 Oct 2002, William Lindley wrote:

> On what legal grounds could I be sued for GPL infringement if I merely
> link to "any library providing function X with parameters Y and Z" ?

If the prosecution could convince the jury that
the library you developed against was in fact a
GPL library, and could also convince that jury
that the GPL's definition of a derivative work
is legally binding even when you're not distributing
the library.

The former seems pretty easy - simply get the
server logs and show that you DL'd the library
in question, and that your code works as if it
ran against an identical API. The jury could easily
be lead to believe that either you coded against
the original library (which is covered by the
GPL), or that you created a library with an
identical API (a derivative (by the GPL's
definition of derivative) work of the original
library, and hence also covered by the GPL).

The latter is the tougher one. Convincing
the jury that without consenting to the GPL
itself(*) you are still bound by its terms would
be a significant uphill struggle.

* You needn't consent to the GPL to view the source
code, and copying the APIs alone may not be
sufficient to imply copyright infringement. You're
not distributing the library or violating traditional
copyright in any other way, so you haven't triggered
the GPL.