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I'm looking for a chart like this:

alt text

Basically something that tells you whether an app with a given license can be linked with a library of a given license.

Does such a thing exist?

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+1 for the hand-drawn example :-) – Dean Harding Jan 5 '11 at 23:40
One caveat: GPL is not necessarily compatible with GPL. – mario Jan 6 '11 at 2:11
@mario: The graph was just an example. – Nathan Osman Jan 6 '11 at 2:19

It's unlikely such a thing, as described, exists: there are many definitions of what constitutes a FOSS license and even more licenses. Such a graph would never be canonical or authoritative.

However, GNU and the Free Software Foundation (and by extension, Wikipedia) have taken great pains to document which licenses are GPL-compatible (and subsequently "FSF-approved"):

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There's a table for various GPL/LGPL versions here too: – Mark H Jan 6 '11 at 0:06
Your logic is a bit confusing to me. It's true that there are quite a lot of licenses, and some are more free than others, but for any given pair of licenses, there is an answer. Such a graph would never be complete, but it could certainly be based on authoritative legal advice. – Jefromi Jan 6 '11 at 6:37
@Jefromi if legal interpretations were clear and unambiguous, there'd be no need for courts, lawyers, or judges. Whether a license is compatible with another is subject to interpretation, and there is no single authoritative source for that interpretation. Even the lists mentioned in my answer and sparkie's comment are the legal opinions of one body, the Free Software Foundation. – user8 Jan 6 '11 at 6:45
The existence of ambiguity doesn't mean that all cases are ambiguous, and most of us don't need absolute authority. For example, the FSF saying a license is GPL-compatible is going to be good enough, even though it's not as absolute as a supreme court ruling. – Jefromi Jan 6 '11 at 6:57
@Jefromi there is no authoritative answer, and a graph is not an alternative to sound legal advice. The only lists that exist are ones that specific bodies have published based on their own interpretation of the legal issues surrounding the licenses they vet. It's why the FSF only talks about specific licenses within the context of its own, normative definition of what a free software license is and makes no claim about others. Licensing is not a simple issue that can be summed up in a graph. – user8 Jan 6 '11 at 7:06

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