I have an affiliate marketing client who needs to know if I can program this. Can I do one or both of the following scenarios without violating the GPL license?
Scenario A:
Make a software installer for a GPL licensed product which includes source, binaries, and license info. The installer also has a checkbox for installing optional software that’s payware. (In this case, the payware is free crippleware, but has a registration upsell to provide more features.) The two products will not share libraries or anything else.
Scenario B:
Same as A, but reversed. So, the installer installs the payware, but there’s a checkbox to also install the GPL software. And, again, when you install the GPL software, it comes with binaries, source, and license info.
You need to more accurately define what you mean by “payware” here; on the face of it it reads as though you’re referring to commercial software, and the GPL itself is actually quite cool about commercial exploitation – there’s nothing to stop your “payware” from also being licensed under the GPL for example, which would side-step the problem entirely.
That aside, I believe that your question is (at least partially) answered by the following GPL FAQ entry: http://www.gnu.org/licenses/gpl-faq.html#MereAggregation
An “aggregate” consists of a number of separate programs, distributed
together on the same CD-ROM or other media. The GPL permits you to
create and distribute an aggregate, even when the licenses of the
other software are non-free or GPL-incompatible. The only condition is
that you cannot release the aggregate under a license that prohibits
users from exercising rights that each program’s individual license
would grant them.
Having the same installer used for both GPL and non-GPL software muddies things a little, but the easy solution seems to be to just use separate installers.
All of this comes with a standard “I am not a lawyer” disclaimer and advice that if you have a legal concern over this then you would be better served by consulting a qualified legal professional than by asking some random guy on the internet.