Maciej Mróz wrote:
However, imagine simple situation:
1. I write proprietary program with open plugin api. I even make the api itself public domain. Program works by itself, does not contain any GPL-ed code.
2. Later someone writes plugin using the api (which is public domain so is GPL compatible), plugin gets loaded into my software, significantly affecting its functionality (UI, operations, file formats, whatever).
3. Someone downloads the plugin and loads it into my program
I believe that in this case, the key is *distribution*.
You are not violating the GPL, because you are not distributing a program that is derived (according to the GPL's definition of derived) from GPL code.
The plugin author *is* distributing GPL-derived code, but is doing so under a GPL license. That's fine too.
The end user is now linking (dynamically) GPL code with your proprietary code. However, he is *not* distributing the linked assemblage. This is allowed under the GPL; its terms only apply when distribution takes place.
If the end user is a repackager, and then turns around and distributes both sets of code together, then that would (potentially) violate GPL terms. But as long as they're not distributed together, then it's okay. This should even extend to distributing a basic (proprietary) plugin and including a document describing where & how to get the more-featureful GPL replacement plugin. (Distributing both programs as separate packages on a single installation medium would be a tricky edge case. I suspect it *could* be done in a GPL-acceptable way, but one would need to take care about it.)
Of course, this is only my own personal interpretation and opinion -- IANAL, TINLA, YMMV, etc, etc.
Jeff Shannon Technician/Programmer Credit International
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