Re: Python library under permissive GPL-compatible license optionally using GPL library

[Ben Finney <ben+debian@benfinney.id.au>]

Yaroslav Halchenko <debian@onerussian.com> writes:

> If we have a library X in Python, released under some GPL-compatible
> license (e.g. BSD-3 or Expat) and then using (optionally) some GPL
> code (at run time) provided by another library Y -- what are the
> implications?

The implications depend on what “using” means. That's a very vague term,
and the specific action will determine whether copyright is invoked.

So, what specific things will the distributor of library Y be doing with
it?

If an action constitutes Y becoming a derivative work of X, then the
copyright of X is invoked and the redistributor must have license
(either from the X copyright holder, or under some fair use exception)
to perform that action.

If an action constitutes X becoming a derivative work of Y, then the
copyright of Y is invoked and the redistributor must have license
(either from the Y copyright holder, or under some fair use exception)
to perform that action.

There may be other possibilities too. It all depends on the specific
actions being done. To “use” doesn't tell us what is being done.

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Ben Finney