On Thu, Dec 22, 2011, at 02:00 PM, Lawrence Rosen wrote: > Linking GPL software to proprietary software is legal as > long as one doesn't create a derivative work.
Thank you for the helpful response. The hard part then is knowing when a derivative work would be formed, or, perhaps more difficultly, what is the derivative work constitutes. (I know the analysis below is too generic to provide any concrete answer, but I'd love to learn more about the frequently misunderstood things about the GPL) Let's say my original work O has been changed via a set of non-trivial modifications M, where these changes provide new/different functionality to the base work O and cannot be used independently. In this case, it seems clear that both M and the combined work, C = O+M are derived works. At this point, if O is licensed under the GPL, to publicly distribute M (and hence C), it should be licensed and distributed under a license compatible with the GPL. Now for the hard part. Suppose there is a proprietary work P which M references and uses for a critical part of its implementation and that P doesn't have any substitutes; that is, the interface between P and M is proprietary, and not a standard protocol with open implementations. Does the GPL prevent the distribution of M if the work it relies upon, P, isn't compatibly licensed? I've heard some GPL advocates say that the answer depends on the type of linking and if M is also derived from P. Frankly, I don't understand either of these limitations, the first is a technical detail. If M doesn't operate as intended without P, why would it matter if M be a derived work of P? As a non-lawyer, I read section 5(c) where it says in order to distribute the modifications M, you must license under GPL "the whole of the work, and all its parts, regardless of how they are packaged". Further, in section 1 of the GPL it states the corresponding source must include "all the source" needed to "run the object code". So, I'm quite confused... it doesn't talk about the type of linking nor does it seem to require that M be derived from P. I do know that I can't operate O+M without P and this seems sufficient to bar the public distribution of M. I suppose it matters on the specifics of the given case. > If GPL advocates insist upon distinguishing among types > of functional linking, then talented software engineers > will avoid disputes by building shims, APIs, or use > dynamic linking to accomplish their functional goals. I absolutely agree with this. It shouldn't matter at all how the components are connected, via direct incorporation, static linking, dynamic linking, or via WebAPIs. Those are simply technical details and attempts to discuss type of linking I think really distracts from the primary concern. Best, Clark _______________________________________________ License-discuss mailing list [email protected] http://projects.opensource.org/cgi-bin/mailman/listinfo/license-discuss
