Does A Software License Cover Patches?

As a followup to the software licensing question on Tuesday, I've decided to open up a topic on the discussion of software patches, software licensing and the relationships between them. How large must a patch become before it isn't considered a patch? If a patch comes with its own license, how does that affect the license of the original program? (Read More)

Sanity asks: "Recently a discussion came up in my company concerning how a modification to a piece of GPL code could be distributed without its authors being forced to place it under the GPL. It seemed to me that if I created a patch to a piece of software (which can be viewed as an algorithm which modifies some source code in a particular way) then I would have the right to put this patch under whatever license I liked. I contacted RMS about this and predictably he claimed that the patch would fall under the GPL -- yet this view implies that software licenses are much more powerful than many people instinctively might think -- and if true, has some frightening implications."

"OK, so I do require the original code to generate this patch, but (assuming the patching software I use is efficient) the patch will not contain any of the original GPL code. The thing is that if this were possible it would render the GPL largely useless. What if I created a patch manually, writing a sophisticated computer program which modified code. Would this program itself fall under the license of the code it modifies? Clearly not -- but where is the line drawn here? Surely this is a Pandora's Box of problems, and it concerns the GPL at a fundamental level."

The big question here is: "How large does a patch need to be before the patched version becomes its own program?" and there really isn't an easy answer to that. It stands to reason that if a program can be patched at the source (not binary) level, then it contains enough of the original code to still be considered a derived work. But would such a definition stand under intense scrutiny?

Frac asks: "I'm thinking about creating a Quake 3 mod. Like LAME, I intend to GPL my patch, so anyone who wants to derive a mod from mine needs to open up their source code. However, the more I think about this, the more I realize that it's not possible to GPL a patch, or license a patch that doesn't agree with the orginal source code in question. In fact, if patches can be GPL'ed, the GPL itself will be open to violation and loopholes.

If someone can creat a GPL'ed patch to a non-GPL'ed source code, why can't someone else creat a, say, artistic license patch that patches the GPL'ed patch? Although GPL virtually prohibits people from adding code that isn't GPL'ed itself, what gives LAME the right to apply GPL to the ISO Dist10 mp3 encoder source code?

I think this is an issue that someone needs to straighten out. If patches can be applied under a license, there's nothing to stop e.g. Sun from coming out with a SCSL patch for the Linux kernel."